NoneType Error When Using `rez pip` on Windows

[mstreatfield]

On Windows (using PowerShell or command prompt), I get a NoneType error when runningrez pip -i pylint (although it doesn't matter which package I try to install).

  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python39\lib\runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python39\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\rez\2.72.0\Scripts\rez\rez.exe\__main__.py", line 7, in <module>
  File "c:\rez\2.72.0\lib\site-packages\rez\cli\_entry_points.py", line 64, in run_rez
    return run()
  File "c:\rez\2.72.0\lib\site-packages\rez\cli\_main.py", line 170, in run
    returncode = run_cmd()
  File "c:\rez\2.72.0\lib\site-packages\rez\cli\_main.py", line 162, in run_cmd
    return func(opts, opts.parser, extra_arg_groups)
  File "c:\rez\2.72.0\lib\site-packages\rez\cli\pip.py", line 70, in command
    pip_install_package(
  File "c:\rez\2.72.0\lib\site-packages\rez\pip.py", line 267, in pip_install_package
    py_exe, context = find_pip(pip_version, python_version)
  File "c:\rez\2.72.0\lib\site-packages\rez\pip.py", line 94, in find_pip
    py_exe, found_pip_version, context = find_pip_from_context(
  File "c:\rez\2.72.0\lib\site-packages\rez\pip.py", line 209, in find_pip_from_context
    proc = context.execute_command(
  File "c:\rez\2.72.0\lib\site-packages\rez\resolved_context.py", line 958, in _check
    return fn(self, *nargs, **kwargs)
  File "c:\rez\2.72.0\lib\site-packages\rez\resolved_context.py", line 1221, in execute_command
    return interpreter.subprocess(args, **Popen_args)
  File "c:\rez\2.72.0\lib\site-packages\rez\rex.py", line 655, in subprocess
    return Popen(args,
  File "c:\rez\2.72.0\lib\site-packages\rez\utils\execution.py", line 85, in __init__
    super(Popen, self).__init__(args, **kwargs)
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python39\lib\subprocess.py", line 947, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python39\lib\subprocess.py", line 1356, in _execute_child
    args = list2cmdline(args)
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python39\lib\subprocess.py", line 561, in list2cmdline
    for arg in map(os.fsdecode, seq):
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python39\lib\os.py", line 822, in fsdecode
    filename = fspath(filename)  # Does type-checking of `filename`.
TypeError: expected str, bytes or os.PathLike object, not NoneType

The problem appears to be that find_python_in_context can return None which is then unhandled in the calling find_pip_from_context.

In my case, find_python_in_context returns None because shutilwhich.which is unable to locate the python executable. While which is looking for python.exe (among other path extensions) the python package I created with rez bind only contains a python executable (symlink) without an extension.

I've created an additional python.exe symlink to work around this for the moment.

[mstreatfield]

This looks to be related to #904.

[herronelou]

possibly related to #1027