tests/sitecustomize.py

remotefilelog: reduce probability of race-condition in remotefilelog tests

ca1014ad3de4 introduced a new parameter `ensurestart` to speed up
remotefilelog background processes start. Unfortunately it seems to have
increased the possibility of race-conditions in remotefilelog tests testing
those background processes.

With `ensurestart=False`, it seems that it's more probable to enter in a race
condition with `debugwaitonprefetch` and `debugwaitonrepack` in remotefilelog
background tests. Our CI seems to have a high probability of triggering this
race condition so make it configurable to ensure tests are stable.

Differential Revision: https://phab.mercurial-scm.org/D6772

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