Ignore signal exception on AutoInterrupt destructor.

When command run as subprocess, AutoInterrupt will kill the
process on destructor. However, if process already finished,
it raise OSError exception.

This fix just ignore OSError on os.kill.

Conflicts:
	git/cmd.py

Author: sugi

git/cmd.py

@@ -87,6 +87,8 @@ def __del__(self):
             # try to kill it
             try:
                 os.kill(self.proc.pid, 2)   # interrupt signal
+            except OSError:
+                pass # ignore error when process already died
             except AttributeError:
                 # try windows 
                 # for some reason, providing None for stdout/stderr still prints something. This is why