Fix erroneous non-ASCII in local version

[zuo]

Closes: #469.

• Fix validation of the given version in the packaging.version.Version's constructor.
• Fix validation of the given spec in the packaging.specifiers.Specifier's constructor.
• Complement relevant tests, including adding cases related to presence of non-ASCII whitespace characters in input strings.
• Fix the docs of packaging.version.VERSION_PATTERN by mentioning necessity
  of the re.ASCII flag.

[zuo]

@pradyunsg @brettcannon

Hmm, the error (some stringEnd vs. string_end discrepancy in an InvalidRequirement's exception message) that is reported by automatic checks seems unrelated to this PR.

=================================== FAILURES ===================================
________________ TestRequirements.test_parseexception_error_msg ________________

self = <tests.test_requirements.TestRequirements object at 0x00007f89be140fe0>

    def test_parseexception_error_msg(self):
        with pytest.raises(InvalidRequirement) as e:
            Requirement("toto 42")
>       assert "Expected stringEnd" in str(e.value)
E       assert 'Expected stringEnd' in 'Parse error at "\'42\'": Expected string_end'

[uranusjr]

I think we also need tests to validate non-ASCII whitespaces are removed correctly.

[zuo]

@uranusjr

I think we also need tests to validate non-ASCII whitespaces are removed correctly.

OK, added.

[zuo]

I am sorry, I miss-clicked so that these 3 workflows become required again. :-(

[pradyunsg]

You didn't misclick -- you did all the right things. :)

It's just that GitHub requires me to click a button every time you modify a PR (It's their way to avoiding cryptomining endevours) to run our checks and I've done that now!

[zuo]

Ah, ok. :-)

[zuo]

What else do I need to do?

[brettcannon]

What else do I need to do?

At this point probably just be patient. We are all busy and so it might be a while until someone has time to review this PR.

[brettcannon]

@zuo I've got time to review this now (sorry about the delay 😅), but there are now merge conflicts. Did you want to update the PR?