def test_killRequestedWithPIDFileEmpty(self):
        """
        L{Runner.killIfRequested} when C{kill} is true and given a C{pidFile}
        containing no value exits with L{ExitStatus.EX_DATAERR}.
        """
        pidFile = PIDFile(DummyFilePath(b""))
        runner = Runner(reactor=MemoryReactor(), kill=True, pidFile=pidFile)
        runner.killIfRequested()

        self.assertEqual(self.exit.status, ExitStatus.EX_DATAERR)
        self.assertEqual(self.exit.message, "Invalid PID file.")

        L{Runner.killIfRequested} when C{kill} is true and given a C{pidFile}
        containing no value exits with L{ExitStatus.EX_DATAERR}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/application/runner/test/test_runner.py