py3: replace file() with open() in test-tag.t
file() is not present in Python 3.
Differential Revision: https://phab.mercurial-scm.org/D2116
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