Locally, these "non-ASCII character in alias" errors don't show up,
though I get them when the alias is defined at the command line rather
than in an hgrc.
The brokenness comes from the fact that hgrcs are parsed with regexes,
and re/re2 differ in this way:
$ python -c 'import re; print(re.compile("(.*)").match("aaa\xc0bbbb").groups())'
$ python -c 'import re2; print(re2.compile("(.*)").match("aaa\xc0bbbb").groups())'
Apparently re2 stops when it encounters invalid utf8 (which I suppose makes sense
given that '.' matches what appears to be a codepoint rather than a byte). This is
presumably a bug in hg, but not very important, so just change the test to stick
to valid utf8.