tox uses wrong virtualenv PATH under MSYS

[jschwartzentruber]

tox assumes that all Windows installations use "{ENV}\Scripts" as the installation folder. This isn't true for MSYS, which uses "{ENV}\bin". If I patch TestenvConfig.get_envbindir() to return "bin" instead of "Scripts", tox uses the correct interpreter.

I believe an exception is needed if MSYSTEM is set in the environment (or I don't know if there's a more "proper" way to detect MSYS), similar to the exception that exists in that function for PyPy.

$ tox -rvv -e py38
using tox.ini: C:/Users/User/source/repos/fuzzfetch/tox.ini (pid 6820)
  removing C:/Users/User/source/repos/fuzzfetch/.tox/log
using tox-3.23.0 from C:/Users/User/Desktop/msys64-JHtqq6ULSEu38CxK8FxfLQ/mingw64/lib/python3.8/site-packages/tox/__init__.py (pid 6820)
skipping sdist step
py38 uses C:/Users/User/Desktop/msys64-JHtqq6ULSEu38CxK8FxfLQ/mingw64/bin/python.exe
py38 start: getenv C:/Users/User/source/repos/fuzzfetch/.tox/py38
py38 cannot reuse: -r flag
py38 recreate: C:/Users/User/source/repos/fuzzfetch/.tox/py38
  removing C:/Users/User/source/repos/fuzzfetch/.tox/py38
setting PATH=C:/Users/User/source/repos/fuzzfetch/.tox/py38/Scripts;C:\Users\User\Desktop\msys64-JHtqq6ULSEu38CxK8FxfLQ\mingw64\bin;C:\Users\User\Desktop\msys64-JHtqq6ULSEu38CxK8FxfLQ\usr\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0;C:\Windows\System32\OpenSSH;C:\Program Files\dotnet;C:\Program Files\Microsoft SQL Server\130\Tools\Binn;C:\Program Files\Microsoft SQL Server\Client SDK\ODBC\170\Tools\Binn;C:\Users\User\AppData\Local\Microsoft\WindowsApps;C:\Users\User\AppData\Local\Programs\Microsoft VS Code\bin;C:\Users\User\.dotnet\tools;C:\Users\User\Desktop\msys64-JHtqq6ULSEu38CxK8FxfLQ\mingw64\bin\
[9056] C:/Users/User/source/repos/fuzzfetch/.tox$ C:/Users/User/Desktop/msys64-JHtqq6ULSEu38CxK8FxfLQ/mingw64/bin/python.exe -m virtualenv --no-download --python C:/Users/User/Desktop/msys64-JHtqq6ULSEu38CxK8FxfLQ/mingw64/bin/python.exe py38
created virtual environment CPython3.8.8.final.0-64 in 532ms
  creator CPython3Windows(dest=C:/Users/User/source/repos/fuzzfetch/.tox/py38, clear=False, no_vcs_ignore=False, global=False)
  seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=C:/Users/User/AppData/Local/pypa/virtualenv)
    added seed packages: pip==21.0.1, setuptools==54.1.2, wheel==0.36.2
  activators BashActivator,BatchActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator
py38 installdeps: freezegun, pytest, pytest-cov, requests-mock
setting PATH=C:/Users/User/source/repos/fuzzfetch/.tox/py38/Scripts;C:\Users\User\Desktop\msys64-JHtqq6ULSEu38CxK8FxfLQ\mingw64\bin;C:\Users\User\Desktop\msys64-JHtqq6ULSEu38CxK8FxfLQ\usr\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0;C:\Windows\System32\OpenSSH;C:\Program Files\dotnet;C:\Program Files\Microsoft SQL Server\130\Tools\Binn;C:\Program Files\Microsoft SQL Server\Client SDK\ODBC\170\Tools\Binn;C:\Users\User\AppData\Local\Microsoft\WindowsApps;C:\Users\User\AppData\Local\Programs\Microsoft VS Code\bin;C:\Users\User\.dotnet\tools;C:\Users\User\Desktop\msys64-JHtqq6ULSEu38CxK8FxfLQ\mingw64\bin\
WARNING: test command found but not installed in testenv
  cmd: C:/Users/User/Desktop/msys64-JHtqq6ULSEu38CxK8FxfLQ/mingw64/bin/python.EXE
  env: C:/Users/User/source/repos/fuzzfetch/.tox/py38
Maybe you forgot to specify a dependency? See also the allowlist_externals envconfig setting.

DEPRECATION WARNING: this will be an error in tox 4 and above!
[5732] C:/Users/User/source/repos/fuzzfetch$ C:/Users/User/Desktop/msys64-JHtqq6ULSEu38CxK8FxfLQ/mingw64/bin/python.EXE -m pip install freezegun pytest pytest-cov requests-mock
Requirement already satisfied: freezegun in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (1.1.0)
Requirement already satisfied: pytest in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (6.2.2)
Requirement already satisfied: pytest-cov in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (2.11.1)
Requirement already satisfied: requests-mock in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (1.8.0)
Requirement already satisfied: python-dateutil>=2.7 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from freezegun) (2.8.1)
Requirement already satisfied: six>=1.5 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from python-dateutil>=2.7->freezegun) (1.15.0)
Requirement already satisfied: py>=1.8.2 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from pytest) (1.10.0)
Requirement already satisfied: toml in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from pytest) (0.10.2)
Requirement already satisfied: iniconfig in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from pytest) (1.1.1)
Requirement already satisfied: atomicwrites>=1.0 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from pytest) (1.4.0)
Requirement already satisfied: packaging in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from pytest) (20.9)
Requirement already satisfied: pluggy<1.0.0a1,>=0.12 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from pytest) (0.13.1)
Requirement already satisfied: colorama in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from pytest) (0.4.4)
Requirement already satisfied: attrs>=19.2.0 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from pytest) (20.3.0)
Requirement already satisfied: coverage>=5.2.1 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from pytest-cov) (5.5)
Requirement already satisfied: requests<3,>=2.3 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from requests-mock) (2.25.1)
Requirement already satisfied: certifi>=2017.4.17 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from requests<3,>=2.3->requests-mock) (2020.12.5)
Requirement already satisfied: urllib3<1.27,>=1.21.1 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from requests<3,>=2.3->requests-mock) (1.26.4)
Requirement already satisfied: chardet<5,>=3.0.2 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from requests<3,>=2.3->requests-mock) (4.0.0)
Requirement already satisfied: idna<3,>=2.5 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from requests<3,>=2.3->requests-mock) (2.10)
Requirement already satisfied: pyparsing>=2.0.2 in c:/users/user/desktop/msys64-jhtqq6ulseu38cxk8fxflq/mingw64/lib/python3.8/site-packages (from packaging->pytest) (2.4.7)
WARNING: test command found but not installed in testenv
  cmd: C:/Users/User/Desktop/msys64-JHtqq6ULSEu38CxK8FxfLQ/mingw64/bin/python.EXE
  env: C:/Users/User/source/repos/fuzzfetch/.tox/py38
Maybe you forgot to specify a dependency? See also the allowlist_externals envconfig setting.

DEPRECATION WARNING: this will be an error in tox 4 and above!
py38 finish: getenv C:/Users/User/source/repos/fuzzfetch/.tox/py38 after 2.28 seconds
py38 start: developpkg C:/Users/User/source/repos/fuzzfetch
py38 develop-inst: C:/Users/User/source/repos/fuzzfetch
--- snip ---

This was already mentioned in msys2/MINGW-packages#7014 and #1648, but those dealt with other upstream packaging issues, and I see no tox issue regarding this specific problem.

Steps to reproduce

Install msys2 and in its bash shell, run pacman -S mingw-w64-x86_64-python mingw-w64-x86_64-python-pip mingw-w64-x86_64-python-wheel, then install latest tox using pip.

The project I've experienced this on is fuzzfetch. Just clone and run tox -e py38.

[gaborbernat]

PRs are welcomed.