Consider removing PEP 723 support, while the PEP is provisional

[pradyunsg]

Describe the bug

pipx currently implements a provisional PEP, PEP 723. This PEP is not meant to be exposed in a user-facing manner at this time and this was explicitly flagged in the PR as well as the discussion linked from the comment there.

How to reproduce

pipx run implements PEP 723, since #1100 was merged in 1.3.0.

Expected behavior

pipx run does not implement PEP 723, until a final decision is made on the PEP.

[pradyunsg]

x-ref the discuss.python.org thread

[dukecat0]

@pradyunsg I've opened #1129 to remove the PEP 723 support temporarily.

[gaborbernat]

I'm strong -1 on this. First, PEP-723 is provisionally accepted; while the alternative PEP-722 is rejected. So, considering this, PEP-723 is the likely winner, and is fine to have an implementation in pipx. Finally, tools are free to implement PEPs not accepted yet; if anything, we had a conversation last year that we are heading to a place where we are accepting PEPs that are never implemented. To stop that going ahead, we would require new PEPs to have at least one implementation live before we accept it. pipx now satisfies this requirement for PEP-723. If the PEP gets amended (or rejected), the implementation in pipx can also be amended (or removed). I consider the current implementation experimental, and not binding as far as backwards compatibility goes.