=== modified file 'IPython/utils/rlineimpl.py'
--- IPython/utils/rlineimpl.py	2009-07-02 17:26:16 +0000
+++ IPython/utils/rlineimpl.py	2009-08-19 21:56:50 +0000
@@ -33,12 +33,17 @@
 uses_libedit = False
 if sys.platform == 'darwin' and have_readline:
     import commands
-    (status, result) = commands.getstatusoutput( "otool -L %s | grep libedit" % _rl.__file__ )
-    if status == 0 and len(result) > 0:
-        # we are bound to libedit - new in Leopard
-        _rl.parse_and_bind("bind ^I rl_complete")
-        print "Leopard libedit detected."
-        uses_libedit = True
+    try:
+        (status, result) = commands.getstatusoutput( "otool -L %s | grep libedit" % _rl.__file__ )
+    except IOError:
+        # Something interfered with reading the output. Probably PyQt4.
+        pass
+    else:
+        if status == 0 and len(result) > 0:
+            # we are bound to libedit - new in Leopard
+            _rl.parse_and_bind("bind ^I rl_complete")
+            print "Leopard libedit detected."
+            uses_libedit = True
 
 
 # the clear_history() function was only introduced in Python 2.4 and is