avoid missing readline warning in zmqshell

InteractiveShell.set_autoindent() warns when readline is missing, and
the zmqshell no longer loads readline.  This changes the condition
of the warning to only if it is being enabled, and prevents enabling
autoindent in the zmqshell.

IPython/core/interactiveshell.py

@@ -472,7 +472,7 b' class InteractiveShell(SingletonConfigurable, Magic):'
 
         If called with no arguments, it acts as a toggle."""
 
-        if not self.has_readline:
+        if value != 0 and not self.has_readline:
             if os.name == 'posix':
                 warn("The auto-indent feature requires the readline library")
             self.autoindent = 0

IPython/zmq/zmqshell.py

@@ -86,6 +86,9 b' class ZMQInteractiveShell(InteractiveShell):'
     # to the terminal frontend.
     colors_force = CBool(True)
     readline_use = CBool(False)
+    # autoindent has no meaning in a zmqshell, and attempting to enable it
+    # will print a warning in the absence of readline.
+    autoindent = CBool(False)
     
     exiter = Instance(ZMQExitAutocall)
     def _exiter_default(self):