TST: Make test_movie_writer_invalid_path locale-agnostic

[StefRe]

PR summary

Filtering on the error message failed on locales different from English (just matching the error in brackets would also do).
No big deal, though, but a bit annoying on Windows were you can't so easily change the locale for a single command to run.

PR checklist

• [N/A] "closes #0000" is in the body of the PR description to link the related issue
• [N/A] new and changed code is tested
• [N/A] Plotting related features are demonstrated in an example
• [N/A] New Features and API Changes are noted with a directive and release note
• [N/A] Documentation complies with general and docstring guidelines

[story645]

I know a merged this so too late 😓 but could these be combined in an or string?

[StefRe]

could these be combined in an or string?

The two match strings could be combined into one string like this:

def test_movie_writer_invalid_path(anim):
    with pytest.raises(
        FileNotFoundError,
        match=r"\[(?:WinError 3|Errno 2)] .*'(?:\\\\foo\\\\bar\\\\aardvark|/foo)'",
    ):
        anim.save("/foo/bar/aardvark/thiscannotreallyexist.mp4",
                  writer=animation.FFMpegFileWriter())

but I think the explicit condition for win32 or else is easier to read and comprehend.