Add job id type assert to jqueue.py

While the changes introduced in previous patches should stop any job
id parameters reaching the queue as strings, add an assertion here to
catch any strings making it through.
Signed-off-by: Hrvoje Ribicic <riba@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>

lib/jqueue.py

 #
 #
 
-# Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Google Inc.
+# Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2014 Google Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -2043,6 +2043,8 @@ class JobQueue(object):
     @return: either None or the job object
 
     """
+    assert isinstance(job_id, int), "Job queue: Supplied job id is not an int!"
+
     job = self._memcache.get(job_id, None)
     if job:
       logging.debug("Found job %s in memcache", job_id)