Another Ruby on Rails Rake assets:precompile error

Question

I'm trying to deploy my Rails 5.0 on heroku after a bundle update. I'm blocked by an issue on assets:precompile

remote: -----> Preparing app for Rails asset pipeline
remote:        Running: rake assets:precompile
remote:        rake aborted!
remote:        Backend must be defined

Following you'll find the whole logs

remote: -----> Using Ruby version: ruby-2.5.3
remote: -----> Installing dependencies using bundler 2.0.1
remote:        Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
remote:        The git source `git://github.com/ankane/searchkick.git` uses the `git` protocol, which transmits data without encryption. Disable this warning with `bundle config git.allow_insecure true`, or switch to the `https` protocol to keep your data secure.
remote:        The git source `git://github.com/audionerd/draper.git` uses the `git` protocol, which transmits data without encryption. Disable this warning with `bundle config git.allow_insecure true`, or switch to the `https` protocol to keep your data secure.
remote:        The git source `git://github.com/rails/rails-observers.git` uses the `git` protocol, which transmits data without encryption. Disable this warning with `bundle config git.allow_insecure true`, or switch to the `https` protocol to keep your data secure.
remote:        The dependency tzinfo-data (>= 0) will be unused by any of the platforms Bundler is installing for. Bundler is installing for ruby but the dependency is only for x86-mingw32, x86-mswin32, x64-mingw32, java. To add those platforms to the bundle, run `bundle lock --add-platform x86-mingw32 x86-mswin32 x64-mingw32 java`.
remote:        Fetching gem metadata from https://rubygems.org/...........
remote:        Fetching git://github.com/rails/rails-observers.git
remote:        Fetching git://github.com/ankane/searchkick.git
remote:        Fetching rake 13.0.1
remote:        Installing rake 13.0.1
remote:        Fetching concurrent-ruby 1.1.6
remote:        Fetching minitest 5.14.1
remote:        Using thread_safe 0.3.6
remote:        Fetching builder 3.2.4
remote:        Installing builder 3.2.4
remote:        Installing minitest 5.14.1
remote:        Installing concurrent-ruby 1.1.6
remote:        Using erubis 2.7.0
remote:        Using mini_portile2 2.4.0
remote:        Fetching crass 1.0.6
remote:        Installing crass 1.0.6
remote:        Fetching rack 2.2.3
remote:        Fetching nio4r 2.5.2
remote:        Installing nio4r 2.5.2 with native extensions
remote:        Installing rack 2.2.3
remote:        Fetching websocket-extensions 0.1.5
remote:        Installing websocket-extensions 0.1.5
remote:        Fetching mini_mime 1.0.2
remote:        Installing mini_mime 1.0.2
remote:        Using execjs 2.7.0
remote:        Fetching ffi 1.13.1
remote:        Installing ffi 1.13.1 with native extensions
remote:        Using active_material 1.4.2
remote:        Fetching jsonapi-renderer 0.2.2
remote:        Installing jsonapi-renderer 0.2.2
remote:        Using formtastic_i18n 0.6.0
remote:        Fetching method_source 1.0.0
remote:        Installing method_source 1.0.0
remote:        Using thor 0.20.3
remote:        Fetching kaminari-core 1.2.1
remote:        Installing kaminari-core 1.2.1
remote:        Using arel 7.1.4
remote:        Fetching tilt 2.0.10
remote:        Installing tilt 2.0.10
remote:        Using babel-source 5.8.35
remote:        Using require_all 1.5.0
remote:        Fetching rb-fsevent 0.10.4
remote:        Installing rb-fsevent 0.10.4
remote:        Using bundler 2.0.1
remote:        Fetching ast 2.4.1
remote:        Installing ast 2.4.1
remote:        Fetching barby 0.6.8
remote:        Installing barby 0.6.8
remote:        Fetching bcrypt 3.1.13
remote:        Installing bcrypt 3.1.13 with native extensions
remote:        Using cancan 1.6.10
remote:        Fetching chartkick 3.3.1
remote:        Installing chartkick 3.3.1
remote:        Using chunky_png 1.3.11
remote:        Using coffee-script-source 1.12.2
remote:        Using ruby-rc4 0.1.5
remote:        Fetching connection_pool 2.2.3
remote:        Installing connection_pool 2.2.3
remote:        Using orm_adapter 0.5.0
remote:        Using systemu 2.6.5
remote:        Fetching multi_json 1.14.1
remote:        Installing multi_json 1.14.1
remote:        Using multipart-post 2.1.1
remote:        Fetching elasticsearch-rails 7.1.0
remote:        Installing elasticsearch-rails 7.1.0
remote:        Fetching raabro 1.3.1
remote:        Installing raabro 1.3.1
remote:        Using hashie 3.6.0
remote:        Using httpclient 2.8.3
remote:        Fetching interactor 3.1.2
remote:        Installing interactor 3.1.2
remote:        Using json 1.8.6
remote:        Fetching jwt 2.2.1
remote:        Installing jwt 2.2.1
remote:        Using multi_xml 0.6.0
remote:        Fetching newrelic_rpm 6.11.0.365
remote:        Installing newrelic_rpm 6.11.0.365
remote:        Fetching oj 3.10.6
remote:        Using pg 0.21.0
remote:        Fetching pg_query 1.2.0
remote:        Installing pg_query 1.2.0 with native extensions
remote:        Installing oj 3.10.6 with native extensions
remote:        Fetching puma 3.12.6
remote:        Installing puma 3.12.6 with native extensions
remote:        Using pusher-signature 0.1.8
remote:        Fetching rack-timeout 0.6.0
remote:        Installing rack-timeout 0.6.0
remote:        Fetching redis 4.2.1
remote:        Installing redis 4.2.1
remote:        Fetching rqrcode_core 0.1.2
remote:        Installing rqrcode_core 0.1.2
remote:        Fetching ruby_http_client 3.5.0
remote:        Installing ruby_http_client 3.5.0
remote:        Using selectize-rails 0.12.6
remote:        Fetching temple 0.8.2
remote:        Installing temple 0.8.2
remote:        Using turbolinks-source 5.2.0
remote:        Fetching wkhtmltopdf-heroku 2.12.5.0
remote:        Installing wkhtmltopdf-heroku 2.12.5.0
remote:        Fetching tzinfo 1.2.7
remote:        Installing tzinfo 1.2.7
remote:        Fetching nokogiri 1.10.9
remote:        Installing nokogiri 1.10.9 with native extensions
remote:        Fetching i18n 1.8.3
remote:        Installing i18n 1.8.3
remote:        Using websocket-driver 0.6.5
remote:        Using mail 2.7.1
remote:        Fetching autoprefixer-rails 9.8.4
remote:        Installing autoprefixer-rails 9.8.4
remote:        Fetching uglifier 4.2.0
remote:        Installing uglifier 4.2.0
remote:        Using rack-test 0.6.3
remote:        Using sprockets 3.7.2
remote:        Using warden 1.2.8
remote:        Fetching request_store 1.5.0
remote:        Installing request_store 1.5.0
remote:        Using heroku-deflater 0.6.3
remote:        Using rack-mount 0.8.3
remote:        Fetching rack-attack 6.3.1
remote:        Installing rack-attack 6.3.1
remote:        Fetching rack-protection 2.0.8.1
remote:        Installing rack-protection 2.0.8.1
remote:        Using select2-rails 4.0.3
remote:        Using haml 4.0.7
remote:        Using babel-transpiler 0.7.0
remote:        Fetching parser 2.7.1.4
remote:        Installing parser 2.7.1.4
remote:        Using coffee-script 2.4.1
remote:        Using combine_pdf 1.0.16
remote:        Fetching macaddr 1.7.2
remote:        Installing macaddr 1.7.2
remote:        Fetching elasticsearch-api 7.8.0
remote:        Installing elasticsearch-api 7.8.0
remote:        Fetching faraday 1.0.0
remote:        Installing faraday 1.0.0
remote:        Using omniauth 1.3.2
remote:        Fetching sassc 2.4.0
remote:        Installing sassc 2.4.0 with native extensions
remote:        Fetching rb-inotify 0.10.1
remote:        Installing rb-inotify 0.10.1
remote:        Fetching get_process_mem 0.2.5
remote:        Installing get_process_mem 0.2.5
remote:        Fetching pusher 1.3.3
remote:        Installing pusher 1.3.3
remote:        Fetching redis-namespace 1.7.0
remote:        Installing redis-namespace 1.7.0
remote:        Fetching rqrcode 1.1.2
remote:        Installing rqrcode 1.1.2
remote:        Fetching sendgrid-ruby 6.2.1
remote:        Installing sendgrid-ruby 6.2.1
remote:        Fetching slim 4.1.0
remote:        Installing slim 4.1.0
remote:        Fetching turbolinks 5.2.1
remote:        Installing turbolinks 5.2.1
remote:        Fetching et-orbi 1.2.4
remote:        Installing et-orbi 1.2.4
remote:        Using activesupport 5.0.7.2
remote:        Fetching sidekiq 6.0.7
remote:        Installing sidekiq 6.0.7
remote:        Using sprockets-es6 0.9.2
remote:        Fetching scout_apm 2.6.7
remote:        Installing scout_apm 2.6.7 with native extensions
remote:        Using uuid 2.3.9
remote:        Fetching elasticsearch-xpack 7.8.0
remote:        Installing elasticsearch-xpack 7.8.0
remote:        Fetching elasticsearch-transport 7.8.0
remote:        Installing elasticsearch-transport 7.8.0
remote:        Fetching faraday_middleware 1.0.0
remote:        Installing faraday_middleware 1.0.0
remote:        Fetching oauth2 1.4.4
remote:        Installing oauth2 1.4.4
remote:        Using sass-listen 4.0.0
remote:        Fetching puma_worker_killer 0.1.1
remote:        Installing puma_worker_killer 0.1.1
remote:        Fetching fugit 1.3.6
remote:        Installing fugit 1.3.6
remote:        Using globalid 0.4.2
remote:        Using activemodel 5.0.7.2
remote:        Using case_transform 0.2
remote:        Fetching arbre 1.2.1
remote:        Installing arbre 1.2.1
remote:        Fetching delayed_job 4.1.8
remote:        Installing delayed_job 4.1.8
remote:        Fetching global 2.0.0
remote:        Installing global 2.0.0
remote:        Fetching jbuilder 2.10.0
remote:        Installing jbuilder 2.10.0
remote:        Fetching pundit 2.1.0
remote:        Installing pundit 2.1.0
remote:        Using rack-api 1.1.0
remote:        Fetching wicked_pdf 1.4.0
remote:        Installing wicked_pdf 1.4.0
remote:        Using rails-dom-testing 2.0.3
remote:        Fetching loofah 2.6.0
remote:        Installing loofah 2.6.0
remote:        Using ruby-saml 1.0.0
remote:        Fetching elasticsearch 7.8.0
remote:        Installing elasticsearch 7.8.0
remote:        Fetching restforce 4.2.2
remote:        Installing restforce 4.2.2
remote:        Using omniauth-oauth2 1.5.0
remote:        Fetching sass 3.7.4
remote:        Installing sass 3.7.4
remote:        Fetching sidekiq-cron 1.2.0
remote:        Installing sidekiq-cron 1.2.0
remote:        Using activejob 5.0.7.2
remote:        Using activerecord 5.0.7.2
remote:        Using activemodel-serializers-xml 1.0.2 from https://github.com/rails/activemodel-serializers-xml (at master@9368963)
remote:        Using rails-observers 0.2.0 from git://github.com/rails/rails-observers.git (at master@389b577)
remote:        Fetching rails-html-sanitizer 1.3.0
remote:        Using searchkick 4.4.0 from git://github.com/ankane/searchkick.git (at master@83fe00b)
remote:        Installing rails-html-sanitizer 1.3.0
remote:        Using omniauth-salesforce 1.0.5
remote:        Fetching kaminari-activerecord 1.2.1
remote:        Installing kaminari-activerecord 1.2.1
remote:        Fetching polyamorous 2.3.0
remote:        Installing polyamorous 2.3.0
remote:        Fetching activerecord-import 1.0.5
remote:        Installing activerecord-import 1.0.5
remote:        Fetching acts_as_list 1.0.1
remote:        Installing acts_as_list 1.0.1
remote:        Using audited 4.6.5 from https://github.com/Akhilesh05/audited (at revisions-revised@4f42fe8)
remote:        Fetching delayed_job_active_record 4.1.4
remote:        Fetching pghero 2.5.1
remote:        Using pluck_to_hash 1.0.2
remote:        Fetching bootstrap-sass 3.4.1
remote:        Installing delayed_job_active_record 4.1.4
remote:        Installing bootstrap-sass 3.4.1
remote:        Installing pghero 2.5.1
remote:        Using actionview 5.0.7.2
remote:        Using actionpack 5.0.7.2
remote:        Fetching kaminari-actionview 1.2.1
remote:        Installing kaminari-actionview 1.2.1
remote:        Using actioncable 5.0.7.2
remote:        Using actionmailer 5.0.7.2
remote:        Fetching active_model_serializers 0.10.10
remote:        Installing active_model_serializers 0.10.10
remote:        Using formtastic 3.1.5
remote:        Using has_scope 0.7.2
remote:        Using railties 5.0.7.2
remote:        Fetching ransack 2.3.0
remote:        Installing ransack 2.3.0
remote:        Using sprockets-rails 3.2.1
remote:        Using draper 2.1.0 from git://github.com/audionerd/draper.git (at rails5@e816e0e)
remote:        Fetching kaminari 1.2.1
remote:        Installing kaminari 1.2.1
remote:        Using responders 2.4.1
remote:        Fetching jquery-rails 4.4.0
remote:        Installing jquery-rails 4.4.0
remote:        Using coffee-rails 4.2.2
remote:        Using jquery-ui-rails 6.0.1
remote:        Fetching lograge 0.11.2
remote:        Installing lograge 0.11.2
remote:        Fetching scenic 1.5.2
remote:        Installing scenic 1.5.2
remote:        Using slim-rails 3.2.0
remote:        Fetching slowpoke 0.3.2
remote:        Installing slowpoke 0.3.2
remote:        Fetching sassc-rails 2.1.2
remote:        Using rails 5.0.7.2
remote:        Fetching js-routes 1.4.9
remote:        Installing sassc-rails 2.1.2
remote:        Installing js-routes 1.4.9
remote:        Using sass-rails 5.0.7
remote:        Fetching inherited_resources 1.10.0
remote:        Installing inherited_resources 1.10.0
remote:        Fetching devise 4.7.2
remote:        Installing devise 4.7.2
remote:        Fetching active_bootstrap_skin 0.1.5
remote:        Installing active_bootstrap_skin 0.1.5
remote:        Using xdan-datetimepicker-rails 2.5.4
remote:        Fetching interactor-rails 2.2.1
remote:        Installing interactor-rails 2.2.1
remote:        Fetching activeadmin 2.4.0
remote:        Installing activeadmin 2.4.0
remote:        Fetching activeadmin_addons 1.7.1
remote:        Installing activeadmin_addons 1.7.1
remote:        Using devise_saml_authenticatable 1.2.2
remote:        Bundle complete! 91 Gemfile dependencies, 175 gems now installed.
remote:        Gems in the groups development and test were not installed.
remote:        Bundled gems are installed into `./vendor/bundle`
remote:        Post-install message from i18n:
remote:        
remote:        HEADS UP! i18n 1.1 changed fallbacks to exclude default locale.
remote:        But that may break your application.
remote:        
remote:        If you are upgrading your Rails application from an older version of Rails:
remote:        
remote:        Please check your Rails app for 'config.i18n.fallbacks = true'.
remote:        If you're using I18n (>= 1.1.0) and Rails (< 5.2.2), this should be
remote:        'config.i18n.fallbacks = [I18n.default_locale]'.
remote:        If not, fallbacks will be broken in your app by I18n 1.1.x.
remote:        
remote:        If you are starting a NEW Rails application, you can ignore this notice.
remote:        
remote:        For more info see:
remote:        https://github.com/svenfuchs/i18n/releases/tag/v1.1.0
remote:        
remote:        Post-install message from sass:
remote:        
remote:        Ruby Sass has reached end-of-life and should no longer be used.
remote:        
remote:        * If you use Sass as a command-line tool, we recommend using Dart Sass, the new
remote:          primary implementation: https://sass-lang.com/install
remote:        
remote:        * If you use Sass as a plug-in for a Ruby web framework, we recommend using the
remote:          sassc gem: https://github.com/sass/sassc-ruby#readme
remote:        
remote:        * For more details, please refer to the Sass blog:
remote:          https://sass-lang.com/blog/posts/7828841
remote:        
remote:        Removing builder (3.2.3)
remote:        Removing tilt (2.0.9)
remote:        Removing sendgrid-ruby (5.3.0)
remote:        Removing rack (2.0.6)
remote:        Removing concurrent-ruby (1.1.5)
remote:        Removing newrelic_rpm (6.2.0.354)
remote:        Removing ruby_http_client (3.3.0)
remote:        Removing wicked_pdf (1.2.1)
remote:        Removing rb-inotify (0.10.0)
remote:        Removing chartkick (3.0.2)
remote:        Removing tzinfo (1.2.5)
remote:        Removing oauth2 (1.4.1)
remote:        Removing global (1.1.0)
remote:        Removing mustermann (1.0.3)
remote:        Removing kaminari-actionview (1.1.1)
remote:        Removing jsonapi-renderer (0.2.0)
remote:        Removing active_model_serializers (0.10.9)
remote:        Removing elasticsearch-api (7.1.0)
remote:        Removing fugit (1.1.8)
remote:        Removing js-routes (1.4.4)
remote:        Removing ransack (2.1.1)
remote:        Removing pundit (2.0.1)
remote:        Removing jquery-rails (4.3.3)
remote:        Removing elasticsearch-rails (6.0.0)
remote:        Removing redis (4.1.0)
remote:        Removing connection_pool (2.2.2)
remote:        Removing uglifier (4.1.20)
remote:        Removing puma (3.12.1)
remote:        Removing raabro (1.1.6)
remote:        Removing autoprefixer-rails (9.5.0)
remote:        Removing delayed_job (4.1.5)
remote:        Removing multi_json (1.13.1)
remote:        Removing activerecord-import (1.0.1)
remote:        Removing request_store (1.4.1)
remote:        Removing slim (4.0.1)
remote:        Removing loofah (2.2.3)
remote:        Removing barby (0.6.6)
remote:        Removing kaminari-activerecord (1.1.1)
remote:        Removing interactor (3.1.1)
remote:        Removing rails-html-sanitizer (1.0.4)
remote:        Removing restforce (3.1.0)
remote:        Removing bootstrap-sass (3.3.7)
remote:        Removing macaddr (1.7.1)
remote:        Removing bcrypt (3.1.12)
remote:        Removing rb-fsevent (0.10.3)
remote:        Removing nio4r (2.3.1)
remote:        Removing wkhtmltopdf-heroku (2.12.4.0)
remote:        Removing rack-timeout (0.4.2)
remote:        Removing lograge (0.10.0)
remote:        Removing acts_as_list (0.9.19)
remote:        Removing activeadmin_addons (1.7.0)
remote:        Removing elasticsearch-transport (7.1.0)
remote:        Removing interactor-rails (2.2.0)
remote:        Removing scenic (1.5.1)
remote:        Removing minitest (5.11.3)
remote:        Removing pusher (1.3.2)
remote:        Removing nokogiri (1.10.1)
remote:        Removing pghero (2.2.0)
remote:        Removing kaminari (1.1.1)
remote:        Removing rack-protection (2.0.5)
remote:        Removing kaminari-core (1.1.1)
remote:        Removing i18n (1.6.0)
remote:        Removing elasticsearch (7.1.0)
remote:        Removing ffi (1.10.0)
remote:        Removing elasticsearch-xpack (7.1.0)
remote:        Removing faraday (0.15.4)
remote:        Removing crass (1.0.4)
remote:        Removing jbuilder (2.8.0)
remote:        Removing rake (12.3.2)
remote:        Removing scout_apm (2.4.24)
remote:        Removing delayed_job_active_record (4.1.3)
remote:        Removing slowpoke (0.2.1)
remote:        Removing websocket-extensions (0.1.3)
remote:        Removing sass (3.7.3)
remote:        Removing oj (3.7.9)
remote:        Removing jwt (2.1.0)
remote:        Removing redis-namespace (1.6.0)
remote:        Removing puma_worker_killer (0.1.0)
remote:        Removing rqrcode (0.10.1)
remote:        Removing mini_mime (1.0.1)
remote:        Removing arbre (1.1.1)
remote:        Removing temple (0.8.1)
remote:        Removing sidekiq-cron (1.1.0)
remote:        Removing et-orbi (1.1.7)
remote:        Removing rack-attack (5.4.2)
remote:        Removing active_bootstrap_skin (0.1.4)
remote:        Removing method_source (0.9.2)
remote:        Removing pg_query (1.1.0)
remote:        Removing sinatra (2.0.5)
remote:        Removing get_process_mem (0.2.3)
remote:        Removing turbolinks (5.2.0)
remote:        Removing faraday_middleware (0.13.1)
remote:        Removing sidekiq (5.2.5)
remote:        Removing devise (4.6.1)
remote:        Removing rails-observers (25eb685d68e8)
remote:        Removing activeadmin (8a597c4370b4)
remote:        Removing inherited_resources (95d1e24d97dd)
remote:        Removing searchkick (7b6ec29cff34)
remote:        Bundle completed (237.94s)
remote:        Cleaning up the bundler cache.
remote: -----> Installing node-v8.10.0-linux-x64
remote: -----> Detecting rake tasks
remote: -----> Preparing app for Rails asset pipeline
remote:        Running: rake assets:precompile
remote:        rake aborted!
remote:        Backend must be defined
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/global-2.0.0/lib/global/base.rb:16:in `configuration'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/global-2.0.0/lib/global/base.rb:62:in `method_missing'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/config/initializers/01_global.rb:2:in `block in <top (required)>'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/global-2.0.0/lib/global/base.rb:12:in `configure'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/config/initializers/01_global.rb:1:in `<top (required)>'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/activesupport-5.0.7.2/lib/active_support/dependencies.rb:287:in `load'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/activesupport-5.0.7.2/lib/active_support/dependencies.rb:287:in `block in load'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/activesupport-5.0.7.2/lib/active_support/dependencies.rb:259:in `load_dependency'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/activesupport-5.0.7.2/lib/active_support/dependencies.rb:287:in `load'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/engine.rb:648:in `block in load_config_initializer'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/activesupport-5.0.7.2/lib/active_support/notifications.rb:166:in `instrument'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/engine.rb:647:in `load_config_initializer'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/engine.rb:612:in `block (2 levels) in <class:Engine>'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/engine.rb:611:in `each'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/engine.rb:611:in `block in <class:Engine>'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/initializable.rb:30:in `instance_exec'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/initializable.rb:30:in `run'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/initializable.rb:55:in `block in run_initializers'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/initializable.rb:44:in `each'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/initializable.rb:44:in `tsort_each_child'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/initializable.rb:54:in `run_initializers'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/application.rb:352:in `initialize!'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/config/environment.rb:5:in `<top (required)>'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/activesupport-5.0.7.2/lib/active_support/dependencies.rb:293:in `require'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/activesupport-5.0.7.2/lib/active_support/dependencies.rb:293:in `block in require'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/activesupport-5.0.7.2/lib/active_support/dependencies.rb:259:in `load_dependency'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/activesupport-5.0.7.2/lib/active_support/dependencies.rb:293:in `require'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/application.rb:328:in `require_environment!'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/railties-5.0.7.2/lib/rails/application.rb:448:in `block in run_tasks_blocks'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/sprockets-rails-3.2.1/lib/sprockets/rails/task.rb:62:in `block (2 levels) in define'
remote:        /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
remote:        Tasks: TOP => environment
remote:        (See full trace by running task with --trace)
remote:        W, [2020-06-24T11:37:54.708802 #2001]  WARN -- : You are setting a key that conflicts with a built-in method OmniAuth::AuthHash::InfoHash#name defined at /tmp/build_09439178a6d10ac20fa79da929f24556/vendor/bundle/ruby/2.5.0/gems/omniauth-1.3.2/lib/omniauth/auth_hash.rb:34. This can cause unexpected behavior when accessing the key as a property. You can still access the key via the #[] method.
remote: 
remote:  !
remote:  !     Precompiling assets failed.
remote:  !
remote:  !     Push rejected, failed to compile Ruby app.
remote: 
remote:  !     Push failed
remote: Verifying deploy...
remote: 
remote: !   Push rejected to xxxxx-xxxxx.
remote: 

Answer 1

Thanks to @Les Nightingill, I found the issue.

It was not directly linked to assets generation, but the probleme was indicated at the first error line in the logs:

global-2.0.0/lib/global/base.rb:16:in `configuration'

After a bundle update, the Global gem was updated to the 2.0, and the configuration syntax has changed.

Correcting this make all works well.