import git fails when current working directory is not accessible

[comzyh]

Very similar to #1319
Steps to reproduce:

$ mkdir /tmp/foo
$ cd /tmp/foo
$ chmod -x .
$ python -c "import git"

Crash with:

Traceback (most recent call last):
  File "/home/comzyh/.local/lib/python3.8/site-packages/git/__init__.py", line 87, in <module>
    refresh()
  File "/home/comzyh/.local/lib/python3.8/site-packages/git/__init__.py", line 76, in refresh
    if not Git.refresh(path=path):
  File "/home/comzyh/.local/lib/python3.8/site-packages/git/cmd.py", line 305, in refresh
    raise ImportError(err)
ImportError: Bad git executable.
The git executable must be specified in one of the following ways:
    - be included in your $PATH
    - be set via $GIT_PYTHON_GIT_EXECUTABLE
    - explicitly set via git.refresh()

All git commands will error until this is rectified.

This initial warning can be silenced or aggravated in the future by setting the
$GIT_PYTHON_REFRESH environment variable. Use one of the following values:
    - quiet|q|silence|s|none|n|0: for no warning or exception
    - warn|w|warning|1: for a printed warning
    - error|e|raise|r|2: for a raised exception

Example:
    export GIT_PYTHON_REFRESH=quiet


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/comzyh/.local/lib/python3.8/site-packages/git/__init__.py", line 89, in <module>
    raise ImportError('Failed to initialize: {0}'.format(exc)) from exc
ImportError: Failed to initialize: Bad git executable.
The git executable must be specified in one of the following ways:
    - be included in your $PATH
    - be set via $GIT_PYTHON_GIT_EXECUTABLE
    - explicitly set via git.refresh()

All git commands will error until this is rectified.

This initial warning can be silenced or aggravated in the future by setting the
$GIT_PYTHON_REFRESH environment variable. Use one of the following values:
    - quiet|q|silence|s|none|n|0: for no warning or exception
    - warn|w|warning|1: for a printed warning
    - error|e|raise|r|2: for a raised exception

Example:
    export GIT_PYTHON_REFRESH=quiet

GitPython: 3.1.20

GitPython will run a git version when importing, but if the current workding dir is not accessible, the Popen clause will fail.

GitPython/git/cmd.py

Line 821 in ef1ef4d

cwd=cwd,

This can be fixed by adding 2 lines after 5b3669e, but I'm not sure if this fix will break some of your assumption.

        # Allow the user to have the command executed in their working dir.
        try:
            cwd = self._working_dir or os.getcwd()  # type: Union[None, str]            
        except FileNotFoundError:
            cwd = None
        if not os.access(cwd, os.X_OK):
            cwd = None

I found this issue when I'm a previliedged user and try to switch user using sudo su <user> and then run a Python script which need a package depending on GitPython.

[Byron]

Thanks a lot, I have added the additional check assuming this fixes the issue described here.