Merged revisions 84582 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/branches/py3k

........
  r84582 | brian.curtin | 2010-09-07 08:24:38 -0500 (Tue, 07 Sep 2010) | 3 lines

  Adjust #8956 to add the bad signal number to the exception message.
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Lib/subprocess.py

@@ -993,7 +993,7 @@ class Popen(object):
             elif sig == signal.CTRL_BREAK_EVENT:
                 os.kill(self.pid, signal.CTRL_BREAK_EVENT)
             else:
-                raise ValueError("Unsupported signal")
+                raise ValueError("Unsupported signal: {}".format(sig))
 
         def terminate(self):
             """Terminates the process