added none check before logging statement (#195)

jobManager.py

@@ -98,13 +98,18 @@ def __manage(self):
                             preVM = self.preallocator.allocVM(job.vm.name)
                         vmms = self.vmms[job.vm.vmms]  # Create new vmms object
 
-                    # Now dispatch the job to a worker
-                    self.log.info("Dispatched job %s:%d to %s [try %d]" %
-                                  (job.name, job.id, preVM.name, job.retries))
+                    if prevVM.name is not None:
+                        self.log.info("Dispatched job %s:%d to %s [try %d]" %
+                                      (job.name, job.id, preVM.name, job.retries))
+                    else:
+                        self.log.info("Unable to pre-allocate a vm for job job %s:%d [try %d]" % (job.name, job.id, job.retries))
+
                     job.appendTrace(
                         "%s|Dispatched job %s:%d [try %d]" %
                         (datetime.utcnow().ctime(), job.name, job.id, job.retries))
 
+
+                    # Now dispatch the job to a worker
                     Worker(
                         job,
                         vmms,