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.

mercurial/sshpeer.py

@@ -70,7 +70,10 b' class sshpeer(wireproto.wirepeer):'
                 (_serverquote(remotecmd), _serverquote(self.path))))
         ui.note(_('running %s\n') % cmd)
         cmd = util.quotecommand(cmd)
-        self.pipeo, self.pipei, self.pipee = util.popen3(cmd)
+
+        # while self.subprocess isn't used, having it allows the subprocess to
+        # to clean up correctly later
+        self.pipeo, self.pipei, self.pipee, self.subprocess = util.popen4(cmd)
 
         # skip any noise generated by remote shell
         self._callstream("hello")

mercurial/util.py

@@ -129,13 +129,17 b' def popen2(cmd, env=None, newlines=False'
     return p.stdin, p.stdout
 
 def popen3(cmd, env=None, newlines=False):
+    stdin, stdout, stderr, p = popen4(cmd, env, newlines)
+    return stdin, stdout, stderr
+
+def popen4(cmd, env=None, newlines=False):
     p = subprocess.Popen(cmd, shell=True, bufsize=-1,
                          close_fds=closefds,
                          stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                          stderr=subprocess.PIPE,
                          universal_newlines=newlines,
                          env=env)
-    return p.stdin, p.stdout, p.stderr
+    return p.stdin, p.stdout, p.stderr, p
 
 def version():
     """Return version information if available."""