tests/sitecustomize.py

errors: restructure formatparse() to clarify conditions a bit

The `similar` list will be calculated only for
`error.UnknownIdentifier`. It was then printed only if `inst.location
is None`, which is true for that exception type, but it's an indirect
condition to rely on.

Also, it looked from the code like it could both report similarities
and print a hint. That would be a little awkward because the
similarity report looks similar to the hint (both are printed within
parentheses). I also added a `elif` to clarify that. I plan to
refactor this more coming patches so the similarity report actually is
a hint.

Differential Revision: https://phab.mercurial-scm.org/D9343

from __future__ import absolute_import
import os

if os.environ.get('COVERAGE_PROCESS_START'):
    try:
        import coverage
        import uuid

        covpath = os.path.join(
            os.environ['COVERAGE_DIR'], 'cov.%s' % uuid.uuid1()
        )
        cov = coverage.coverage(data_file=covpath, auto_data=True)
        cov._warn_no_data = False
        cov._warn_unimported_source = False
        cov.start()
    except ImportError:
        pass