Rez pip fails to execute in Windows after 2.94.0

[salvaom]

After 2.94.0 the rez pip command will result in an error on Windows when using powershell as the default shell.

I used the following command to test it: pip --install PySide6. You can clearly see the why on the rez-shell.ps1 script:

2.93.0

. "C:\Users\Salva\AppData\Local\Temp\rez_context_x0vn7fvx\context.ps1"
Function prompt {"[rez] $(Get-Location)> "}
$Env:PATHEXT = ((($Env:PATHEXT + ";.PY") -split ";") | Select-Object -Unique) -join ";"
h:\cache\skg\cache\python\3.7.7\5b53\a\python\python.exe -m pip install --use-pep517 --target=C:\Users\Salva\AppData\Local\Temp\pip-e5a3zl2z-rez PySide6
exit $LastExitCode

2.94.0

. "C:\Users\Salva\AppData\Local\Temp\rez_context_d71nj_ag\context.ps1"
Function prompt {"[rez] $(Get-Location)> "}
$Env:PATHEXT = ((($Env:PATHEXT + ";.PY") -split ";") | Select-Object -Unique) -join ";"
"h:\cache\skg\cache\python\3.7.7\5b53\a\python\python.exe" -m pip install --use-pep517 "--target=C:\Users\Salva\AppData\Local\Temp\pip-gbk3dqgz-rez" PySide6
exit $LastExitCode

Yielding the following error:

16:15:24 INFO     Installing 'PySide6' with pip taken from 'h:\\cache\\skg\\cache\\python\\3.7.7\\5b53\\a\\python\\python.exe'
At C:\Users\Salva\AppData\Local\Temp\rez_context_d71nj_ag\rez-shell.ps1:4 char:60
+ "h:\cache\skg\cache\python\3.7.7\5b53\a\python\python.exe" -m pip ins ...
+                                                            ~~
Unexpected token '-m' in expression or statement.
At C:\Users\Salva\AppData\Local\Temp\rez_context_d71nj_ag\rez-shell.ps1:4 char:63
+ ... cache\skg\cache\python\3.7.7\5b53\a\python\python.exe" -m pip install ...
+                                                               ~~~
Unexpected token 'pip' in expression or statement.
    + CategoryInfo          : ParserError: (:) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : UnexpectedToken

Adding a . before the command itself fixes the issue as powershell is then aware that the string is to be executed as a command, same as with the sourcing of the context on the first line of both scripts.

[nerdvegas]

Ah, this looks like it's almost certainly been caused by #1115. Seems like quoting that python exe is causing pwsh to not recognise it as a command?

I'll make this priority, I'm doing some more dev start of next week and will look at this then, thx.