sshpeer: store subprocess so it cleans up correctly When running 'hg pull --rebase', I was seeing this exception 100% of the time as the python process was closing down: Exception TypeError: TypeError("'NoneType' object is not callable",) in <bound method Popen.__del__ of <subprocess.Popen object at 0x937c10>> ignored By storing the subprocess on the sshpeer, the subprocess seems to clean up correctly, and I no longer see the exception. I have no idea why this actually works, but I get a 0% repro if I store the subprocess in self.subprocess, and a 100% repro if I store None in self.subprocess. Possibly related to issue 2240.