nest try/except to catch KeyboardInterrupt in kernel

pyzmq issue 130 means that KeyboardInterrupts are not
properly caught by a single try/except, but must be
nested in two levels.

IPython/zmq/ipkernel.py

@@ -165,8 +165,14 b' class Kernel(Configurable):'
                 # reason for this to be anything less than ~ 0.1s
                 # since it is a real poller and will respond
                 # to events immediately
-                poller.poll(10*1000*self._poll_interval)
-                self.do_one_iteration()
+                
+                # double nested try/except, to properly catch KeyboardInterrupt
+                # due to pyzmq Issue #130
+                try:
+                    poller.poll(10*1000*self._poll_interval)
+                    self.do_one_iteration()
+                except:
+                    raise
             except KeyboardInterrupt:
                 # Ctrl-C shouldn't crash the kernel
                 io.raw_print("KeyboardInterrupt caught in kernel")