def postClassCleanup(self):
        """
        Called by L{unittest.TestCase} after the last test in a C{TestCase}
        subclass. Ensures the reactor is clean by murdering the threadpool,
        catching any pending
        L{DelayedCall<twisted.internet.base.DelayedCall>}s, open sockets etc.
        """
        selectables = self._cleanReactor()
        calls = self._cleanPending()
        if selectables or calls:
            aggregate = DirtyReactorAggregateError(calls, selectables)
            self.result.addError(self.test, Failure(aggregate))
        self._cleanThreads()

        Called by L{unittest.TestCase} after the last test in a C{TestCase}
        subclass. Ensures the reactor is clean by murdering the threadpool,
        catching any pending
        L{DelayedCall<twisted.internet.base.DelayedCall>}s, open sockets etc.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/util.py