Why does this Rails app fails to deploy to GCLOUD?

Question

While attempting to deploy a non-default service to gcloud application with the command:

$ gcloud app deploy

I get the error (right after all gems finish installing):

...
Step #1: /opt/rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/google-api-client- 
0.36.4/lib/google/apis/core/http_command.rb:228:in `check_status': forbidden: The caller does 
not have permission (Google::Apis::ClientError)
....

Step #1:    from /opt/rbenv/versions/2.4.1/bin/rcloadenv:22:in `<main>'
Step #1: The command '/bin/sh -c gem install rcloadenv && rbenv rehash && rcloadenv flex-env- 
config >> .env' returned a non-zero code: 1
Finished Step #1
ERROR
ERROR: build step 1 "gcr.io/cloud- 
builders/docker@sha256:853164af9dfd5ea4613401df48ad77b61bcb2c101b4e5de261c8300ecdd6eb47" 
failed: exit status 1

Note that I performed this process for another service (default) minutes before this one, which tells me my local configuration is working to some extent. Could I be missing any extra step specific to a Rails Application ?

app.yaml

entrypoint: bundle exec rackup --port $PORT
env: flex
runtime: ruby
service: api

runtime_config:
  dotenv_config: flex-env-config

automatic_scaling:
  min_instances: 0
  min_idle_instances: 0

env_variables:
  SECRET_KEY_BASE: <redacted-key>

beta_settings:
  cloud_sql_instances: <redacted-instance-info>

Answer 1

The error got fixed and deployment succeeded when removed this lines from app.yaml :

...
runtime_config:
  dotenv_config: flex-env-config
...

Not sure why this lines were important in the first place, investigate further and update with more meaningful explanation.