def processEnded(self, reason):
        """
        If the process ends with L{error.ProcessDone}, this method calls the
        L{IProtocol} provider's L{connectionLost} with a
        L{error.ConnectionDone}

        @see: L{ProcessProtocol.processEnded}
        """
        if (reason.check(error.ProcessDone) == error.ProcessDone) and (
                reason.value.status == 0):
            return self.protocol.connectionLost(
                Failure(error.ConnectionDone()))
        else:
            return self.protocol.connectionLost(reason)

        If the process ends with L{error.ProcessDone}, this method calls the
        L{IProtocol} provider's L{connectionLost} with a
        L{error.ConnectionDone}

        @see: L{ProcessProtocol.processEnded}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/endpoints.py