mq: avoid silent failure when single patch doesn't apply (issue4604) The error-handling here is quite byzantine. self._apply raises an AbortNoCleanup, but self.apply was swallowing the exception and returns 2. In self.push, we catch all exceptions.. and cleanup. We try to print a message to clean up.. but that relies on having a top-of-stack. Instead, we re-raise the abort in self.apply, and avoid cleanup on AbortNoCleanup in self.push by adding a trivial new except clause. We also modernize the now-visible abort message.