find_pip_from_context failing on Windows platform

[theceebee]

The recent changes to the rez pip module have broken pip installs on Windows,

https://github.com/nerdvegas/rez/blob/6db191f4aa01903e22955cf38e8342cb8697a499/src/rez/pip.py#L162

When doing a context.which call to find the python executable the major version token is being appended to 'python' which on Windows returns None.

This causes an issue with the subsequent subprocess call which attempts to find a pip install.

[JeanChristopheMorinRodeoFX]

Hi @theceebee , thanks for the report. I'm the one who changed this part of the code but I only work in OSX and Linux. I'm being told by @instinct-vfx that the executable with a version in its name on Windows only exists in Python 3. 😐 Someone (me or @instinct-vfx probably) will create a PR shortly to fix this.

[theceebee]

Fantastic. I'll keep an eye out.

[JeanChristopheMorinPerso]

@theceebee If you want to test, you can test with #798 . Just checkout and install and see how it goes.