tests/sitecustomize.py

narrow: fix flaky behavior described in issue6150

This has been plaguing the CI for a good while, and it doesn't appear to have
an easy fix proposed yet. The solution in this change is to always do an
unambiguous (but expensive) lookup in case of comparison. This should always
be correct, albeit suboptimal.

Differential Revision: https://phab.mercurial-scm.org/D10034

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