flaky decorator

flaky.py

def flaky(count=3, os_version=None):
    """
    A decorator generator to retry a test if it fails in one of the OS from
    `os_version`.

    When `os_version` is None it will retry on any OS.

    It will not work with any tests.

    The setUp and tearDown is only called once and not called between
    retries.

    The cleanups are called between retries.
    """
    def decorator(test_item):
        """
        This is the actual decorator.
        """

        @wraps(test_item)
        def wrapper(self):
            """
            Wrap the test method to execute it multiple times.
            """
            error = None
            for _ in range(count):  # pragma: no branch
                try:
                    test_item(self)
                    # All good. Stop trying.
                    return
                except AssertionError as error:  # noqa:cover
                    if (
                        os_version and
                        ServerTestCase.os_version not in os_version
                            ):
                        # The current OS is not targed as flaky, so fail
                        # right away.
                        raise error
                    try:
                        # Run cleanup and try again.
                        self.callCleanup()
                    except Exception:
                        """
                        Just ignore any cleanup error which occurred for a
                        failed tests.

                        If the tests succeeds, the cleanup is not called
                        from here, but as part of the normal test run.
                        """
                    # Let the other thread to execute.
                    time.sleep(0.5)

            # We tried 3 times and still got a failure.
            raise error  # noqa:cover

        return wrapper

    return decorator