Add more informative message around json api mismatch imports.

IPython/parallel/apps/ipcontrollerapp.py

@@ -33,6 +33,9 b' from multiprocessing import Process'
 import zmq
 from zmq.devices import ProcessMonitoredQueue
 from zmq.log.handlers import PUBHandler
+
+# Note: use our own import to work around jsonlib api mismatch.  When these
+# changes propagate to zmq, revert back to the following line instead:
 #from zmq.utils import jsonapi as json
 from IPython.zmq import jsonapi as json
 

IPython/zmq/entry_point.py

@@ -11,6 +11,9 b' import sys'
 import tempfile
 
 # System library imports
+
+# Note: use our own import to work around jsonlib api mismatch.  When these
+# changes propagate to zmq, revert back to the following line instead:
 #from zmq.utils import jsonapi as json
 from IPython.zmq import jsonapi as json