Show pip version warning at top of command output

[oTree-org]

No description provided.

[uranusjr]

LGTM (if the linter error is fixed).

Note that this would change the behaviour of pip install -U pip. Previously check was done after installation, but now it wou emit a warning first, and then proceed to upgrade pip to the latest version. There isn’t really a reliable way to check for that (pip can be upgraded/downgraded by another package as a dependency), so this is probably the best we can do.

[pradyunsg]

TBH, we can probably skip the warning if pip is mentioned as a top-level requirement. That'll cover the pip install -U pip use case, and that's basically the only one that matters TBH.

[hugovk]

Remove whitespace to fix linting:

Suggested change

	self.handle_pip_version_check(options)
	self.handle_pip_version_check(options)

[pradyunsg]

Hmm... I'm wary of doing it like this -- if this consistently fails or raises an error, then the user would basically not be able to use pip in any way.

[pfmoore]

Agreed. If (for example) a user has no internet, they should still be able to use pip offline. A network error in the check shouldn't kill pip.

We should probably:

1. Catch and suppress any errors from this check.
2. Add tests to ensure that we did so successfully.

Maybe the contract for handle_pip_version_check should simply say that it will never generate an exception? I've been playing with Rust recently, so my brain translates this as "the function should just not return a Result" but it's harder to enforce such constraints in Python 🙁

[pradyunsg]

FWIW, I'm also not sure that this is the correct thing to do TBH. The message being at the end of the output is a good thing when you have an install run that spewed out a lot of data.

[pfmoore]

TBH, I don't have a strong opinion about this either way. I suspect that whatever we do with the message, there will always be a certain proportion of people who hate it, so I don't think it's worth putting a lot of effort into improving it. Ultimately, it does the job of making people aware of the need to keep pip updated, and that's the key thing for me.

[pradyunsg]

Going to go ahead and close this, since (1) it has merge conflicts that haven't been resolved in a while and (2) there doesn't seem to be much interest in this idea.

That said, thanks @oTree-org for filing this PR! ^>^