0.971: InvocationError and MYPYPATH issue when running "mypy src" with Tox on GitHub Actions

[jakob-bagterp]

Bug Report
With 0.961 and earlier versions, I used MyPy with Tox on GitHub Actions to run automated tests for three different projects. It has worked without issues, but after upgrading version 0.971, I'm getting an InvocationError even though I'm using the same basic mypy src command to scan my files across all projects.

Bug reports from GitHub Actions:

• Browserist
• Colorist for Python
• Timer for Python

Note that when running version 0.971 on my local machine, I experience no issues:

To Reproduce

1. Run MyPy version 0.971 with Tox on GitHub Actions
2. Use command mypy src

Expected Behavior
MyPy should scan the code and exit without issues.

Actual Behavior
Error message:

/home/runner/work/name-of-project/name-of-project is in the MYPYPATH. Please remove it.

Your Environment

• Mypy version used: 0.971
• Mypy command-line flags: See configuration below
• Python version used: 3.10
• Operating system and version: Ubuntu via GitHub Actions
• MyPy configuration options from setup.cfg:

[mypy]
mypy_path = $MYPY_CONFIG_FILE_DIR/src
disallow_any_unimported = True
no_implicit_reexport = True
show_error_codes = True
strict = True
warn_unreachable = True

• MyPy configuration options from tox.ini:

[testenv:mypy]
basepython = python3.10
deps =
    -r{toxinidir}/requirements_dev.txt
commands = mypy src

[hauntsaninja]

Thanks, duplicate of #13214
I fixed on master and asked for a release with the patch here: #13089 (comment)