BUG: Don't use readline in the ZMQShell.

Closes gh-617.

IPython/core/interactiveshell.py

@@ -108,6 +108,11 b' def softspace(file, newvalue):'
 
 def no_op(*a, **kw): pass
 
+class NoOpContext(object):
+    def __enter__(self): pass
+    def __exit__(self, type, value, traceback): pass
+no_op_context = NoOpContext()
+
 class SpaceInInput(Exception): pass
 
 class Bunch: pass
@@ -242,6 +247,15 b' class InteractiveShell(SingletonConfigurable, Magic):'
                              default_value=get_default_colors(), config=True,
         help="Set the color scheme (NoColor, Linux, or LightBG)."
     )
+    colors_force = CBool(False, help=
+        """
+        Force use of ANSI color codes, regardless of OS and readline
+        availability.
+        """
+        # FIXME: This is essentially a hack to allow ZMQShell to show colors
+        # without readline on Win32. When the ZMQ formatting system is
+        # refactored, this should be removed.
+    )
     debug = CBool(False, config=True)
     deep_reload = CBool(False, config=True, help=
         """
@@ -1636,10 +1650,12 b' class InteractiveShell(SingletonConfigurable, Magic):'
             self.has_readline = False
             self.readline = None
             # Set a number of methods that depend on readline to be no-op
+            self.readline_no_record = no_op_context
             self.set_readline_completer = no_op
             self.set_custom_completer = no_op
             self.set_completer_frame = no_op
-            warn('Readline services not available or not loaded.')
+            if self.readline_use:
+                warn('Readline services not available or not loaded.')
         else:
             self.has_readline = True
             self.readline = readline

IPython/core/magic.py

@@ -2496,7 +2496,8 b' Currently the magic system has the following functions:\\n"""'
 
         import IPython.utils.rlineimpl as readline
 
-        if not readline.have_readline and sys.platform == "win32":
+        if not shell.colors_force and \
+                not readline.have_readline and sys.platform == "win32":
             msg = """\
 Proper color support under MS Windows requires the pyreadline library.
 You can find it at:
@@ -2510,7 +2511,7 b' Defaulting color scheme to \'NoColor\'"""'
             warn(msg)
         
         # readline option is 0
-        if not shell.has_readline:
+        if not shell.colors_force and not shell.has_readline:
             new_scheme = 'NoColor'
             
         # Set prompt colors

IPython/zmq/zmqshell.py

@@ -84,13 +84,8 b' class ZMQInteractiveShell(InteractiveShell):'
     # Override the traitlet in the parent class, because there's no point using
     # readline for the kernel. Can be removed when the readline code is moved
     # to the terminal frontend.
-
-    # FIXME.  This is disabled for now, even though it may cause problems under
-    # Windows, because it breaks %run in the Qt console.  See gh-617 for more
-    # details.  Re-enable once we've fully tested that %run works in the Qt
-    # console with syntax highlighting in tracebacks.
-    # readline_use = CBool(False)
-    # /FIXME
+    colors_force = CBool(True)
+    readline_use = CBool(False)
     
     exiter = Instance(ZMQExitAutocall)
     def _exiter_default(self):