ModuleNotFoundError: No module named 'flake8'

Question

here is the part of the files that are important for this question:

.
├── .env
├── tox.ini
├── requirements-dev.txt
└── tests/
    ├── test_blocking.py
    └── test_async.py

.env example

token = # Replace this with your API token
base_url = # Proxy server to handle requests to API due to IP limitations

tox.ini

[tox]
envlist = py35,py36,py37,py38

[testenv]
changedir = tests
deps = -r{toxinidir}/requirements-dev.txt
sitepackages = true
whitelist_externals =
    flake8
    pytest
commands =
    flake8
    pytest
passenv =
    token
    base_url

[flake8]
max-line-length=120
exclude = __init__.py,.tox
ignore = E252,E302,E731,W605

requirements-dev.txt

asynctest
flake8
pluggy>=0.12.0,<1.0.0
pytest
pytest-asyncio
python-dotenv
tox-travis

with files from tests/ everything is OK, they work on other versions

if, from the project's home directory, in cmd I run such a command tox -e py38

I get this output:

GLOB sdist-make: C:\Python\projects\brawlstats\setup.py
py38 inst-nodeps: C:\Python\projects\brawlstats\.tox\.tmp\package\1\brawlstats-4.0.3.zip
py38 installed: absl-py==0.9.0,aiohttp==3.6.2,alabaster==0.7.12,altgraph==0.17,apng==0.3.4,appdirs==1.4.3,argh==0.26.2,asgiref==3.2.3,astroid==2.3.3,astunparse==1.6.3,async-timeout==3.0.1,asynctest==0.13.0,atomicwrites==1.3.0,attrs==19.3.0,audio2numpy==0.1.2,autopep8==1.5.1,Babel==2.8.0,backcall==0.1.0,bandit==1.6.2,beautifulsoup4==4.9.0,bleach==3.1.4,blis==0.4.1,brawlstats==4.0.3,bs4==0.0.1,cachetools==4.0.0,catalogue==1.0.0,certifi==2019.11.28,cfgv==3.1.0,chardet==3.0.4,click==7.1.1,colorama==0.4.1,colorlog==4.1.0,colour==0.1.5,cPython==0.0.5,cycler==0.10.0,cymem==2.0.3,decorator==4.4.1,defusedxml==0.6.0,distlib==0.3.0,Django==3.0.3,dnspython==1.16.0,docutils==0.16,dodgy==0.2.1,EasyProcess==0.2.10,entrypoint2==0.2,entrypoints==0.3,eventlet==0.25.2,fbs==0.8.6,feedparser==5.2.1,ffmpeg==1.4,filelock==3.0.12,flake8==3.8.3,flake8-polyfill==1.0.2,future==0.18.2,futures==3.1.1,gast==0.3.3,gitdb2==2.0.6,GitPython==2.1.15,google-api-core==1.16.0,google-api-python-client==1.8.2,google-auth==1.11.3,google-auth-httplib2==0.0.3,google-auth-oauthlib==0.4.1,google-cloud-core==1.3.0,google-cloud-translate==2.0.1,google-pasta==0.2.0,googleapis-common-protos==1.51.0,googletrans==2.4.0,goslate==1.5.1,greenlet==0.4.16,grpcio==1.27.2,h5py==2.10.0,httplib2==0.15.0,identify==1.4.11,idna==2.9,imagesize==1.2.0,ipykernel==5.2.1,ipython==7.13.0,ipython-genutils==0.2.0,isort==4.3.21,jedi==0.17.0,Jinja2==2.11.2,json5==0.9.4,jsonschema==3.2.0,jupyter-client==6.1.3,jupyter-core==4.6.3,jupyterlab==2.1.1,jupyterlab-server==1.1.1,Keras-Preprocessing==1.1.2,kivy-deps.angle==0.1.10,kivy-deps.glew==0.1.12,kivy-deps.gstreamer==0.1.18,kivy-deps.sdl2==0.1.23,Kivy-Garden==0.1.4,kiwisolver==1.1.0,lazy-object-proxy==1.4.3,livereload==2.6.2,llvmlite==0.33.0,lxml==4.5.0,macholib==1.14,mando==0.6.4,Markdown==3.2.2,MarkupSafe==1.1.1,matplotlib==3.1.3,mccabe==0.6.1,mistune==0.8.4,monotonic==1.5,more-itertools==8.2.0,mss==5.0.0,multidict==4.7.5,murmurhash==1.0.2,mypy==0.782,mypy-extensions==0.4.3,nbconvert==5.6.1,nbformat==4.4.0,networkx==2.4,nodeenv==1.3.5,notebook==6.0.3,Nuitka==0.6.8.4,numba==0.50.0,numpy==1.18.1,oauth2client==4.1.3,oauthlib==3.1.0,opencv-python==4.2.0.32,opt-einsum==3.2.1,packaging==20.3,pandas==1.0.3,pandocfilters==1.4.2,parso==0.7.0,pathtools==0.1.2,pbr==5.4.5,pefile==2019.4.18,pep8==1.7.1,pep8-naming==0.4.1,pickleshare==0.7.5,Pillow==7.0.0,plac==1.1.3,plotly==4.8.0,pluggy==0.13.1,port-for==0.3.1,pre-commit==2.2.0,preshed==3.0.2,progress==1.4,prometheus-client==0.7.1,prompt-toolkit==3.0.5,prospector==1.2.0,protobuf==3.11.3,py==1.8.1,pyasn1==0.4.8,pyasn1-modules==0.2.8,pycodestyle==2.6.0,pydocstyle==5.0.2,PyDrive==1.3.1,pydub==0.23.1,pyflakes==2.2.0,pygame==1.9.6,pyglet==1.5.2,Pygments==2.6.1,PyInstaller==3.4,pylama==7.7.1,pylint==2.4.4,pylint-celery==0.3,pylint-django==2.0.12,pylint-flask==0.6,pylint-plugin-utils==0.6,pymongo==3.10.1,pynput==1.6.6,pyparsing==2.4.6,pypiwin32==223,PyQt-builder==1.2.0,PyQt5==5.13.2,PyQt5-sip==12.7.1,pyqt5-tools==5.13.2.1.6rc1,pyrsistent==0.16.0,pyscreenshot==1.0,PySimpleGUI==4.18.0,pytest==5.4.1,pytest-asyncio==0.14.0,python-box==4.2.2,python-dateutil==2.8.1,python-dotenv==0.12.0,python-statemachine==0.8.0,pytz==2019.3,pywin32==227,pywin32-ctypes==0.2.0,pywinpty==0.5.7,PyYAML==5.3,pyzmq==19.0.0,qimage2ndarray==1.8.3,radon==4.0.0,requests==2.23.0,requests-oauthlib==1.3.0,requirements-detector==0.7,retrying==1.3.3,rope==0.16.0,rsa==4.0,rstcheck==3.3.1,ruamel.yaml==0.16.10,ruamel.yaml.clib==0.2.0,scipy==1.4.1,selenium==3.141.0,Send2Trash==1.5.0,setoptconf==0.2.0,simpleaudio==1.0.4,sip==5.1.1,six==1.14.0,smmap==3.0.4,smmap2==3.0.1,snowballstemmer==2.0.0,soupsieve==2.0,spacy==2.2.4,Sphinx==3.1.1,sphinx-autobuild==0.7.1,sphinxcontrib-applehelp==1.0.2,sphinxcontrib-devhelp==1.0.2,sphinxcontrib-htmlhelp==1.0.3,sphinxcontrib-jsmath==1.0.1,sphinxcontrib-qthelp==1.0.3,sphinxcontrib-serializinghtml==1.1.4,sqlparse==0.3.0,srsly==1.0.2,stevedore==2.0.1,tabulate==0.8.7,tensorboard==2.2.1,tensorboard-plugin-wit==1.6.0.post3,tensorflow==2.2.0,tensorflow-estimator==2.2.0,tensorflow-hub==0.8.0,termcolor==1.1.0,terminado==0.8.3,testpath==0.4.4,thinc==7.4.0,tkcalendar==1.6.1,toml==0.10.0,tornado==6.0.4,tox==3.14.5,tox-travis==0.12,tqdm==4.46.0,traitlets==4.3.3,translate==3.5.0,typed-ast==1.4.1,typing-extensions==3.7.4.2,uritemplate==3.0.1,urllib3==1.25.8,virtualenv==20.0.15,vk-api==11.8.0,wasabi==0.6.0,watchdog==0.10.3,wcwidth==0.1.9,webencodings==0.5.1,Werkzeug==1.0.1,wily==1.16.0,wrapt==1.11.2,wxPython==4.0.7.post2,yarl==1.4.2
py38 run-test-pre: PYTHONHASHSEED='87'
py38 run-test: commands[0] | flake8
Traceback (most recent call last):
  File "c:\program files\python38\lib\runpy.py", line 193, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "c:\program files\python38\lib\runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "C:\Users\ASUS\AppData\Roaming\Python\Python38\Scripts\flake8.EXE\__main__.py", line 4, in <module>
ModuleNotFoundError: No module named 'flake8'
ERROR: InvocationError for command 'C:\Users\ASUS\AppData\Roaming\Python\Python38\Scripts\flake8.EXE' (exited with code 1)
_________________________________________________________________________________ summary _________________________________________________________________________________
ERROR:   py38: commands failed

also if i run pip3.8 show flake8

I get this output:

Name: flake8
Version: 3.8.3
Summary: the modular source code checker: pep8 pyflakes and co
Home-page: https://gitlab.com/pycqa/flake8
Author: Tarek Ziade
Author-email: tarek@ziade.org
License: MIT
Location: c:\users\asus\appdata\roaming\python\python38\site-packages
Requires: pycodestyle, mccabe, pyflakes
Required-by: flake8-polyfill

what am I doing wrong? on py 3.7 everything works fine. maybe my tox is bad? what should I do? please, help!

Answer 1

My compliments on such an extensive report. Your issue lies probably in this weird setup you've got going on.

# This alows for packages to be accessed from the **globally** installed Python (NOT the tox env). 
sitepackages = True
# This alows for commands to be used available outside tox. Typically used for non-python callables. 
whitelist_externals =
    flake8
    pytest
# Redundant || the context change is confusing - try to use everything from the project root. 
changedir = tests

• sitepackages config value
• changedir
• whitelist externals

So in short you're not using the tox dependencies. You're trying to use global packages and not the ones that tox installed. This, some conjecture, probably lead to some import conflict in python 3.8 globally available packages.

Try the following:

[tox]
envlist = py35,py36,py37,py38

[testenv]
deps = -r{toxinidir}/requirements-dev.txt
commands =
    flake8 {{folders}}
    pytest 
passenv =
    token
    base_url

[flake8]
max-line-length=120
exclude = __init__.py
ignore = E252,E302,E731,W605

PS. Replace {{folders}} with whatever your directory(ies) off code are, usually easier than excluding all kinds of dirs (that might be autogenerated in the future). I typically have flake8 src tests .