'Run check_coverage.py and run its return value.'

def check(self, perfect_files=None):

    coverage_file = (self._testdir.tmpdir / 'coverage.xml')
    if (perfect_files is None):
        perfect_files = [(None, 'module.py')]
    argv = [sys.argv[0]]
    self._monkeypatch.setattr(check_coverage.sys, 'argv', argv)
    with self._testdir.tmpdir.as_cwd():
        with coverage_file.open(encoding='utf-8') as f:
            return check_coverage.check(f, perfect_files=perfect_files)
