Initialise threads for pygtk input hook

IPython/terminal/pt_inputhooks/gtk.py

@@ -39,6 +39,9 b' from __future__ import absolute_import'
 
 import gtk, gobject
 
+# Enable threading in GTK. (Otherwise, GTK will keep the GIL.)
+gtk.gdk.threads_init()
+
 def inputhook(context):
     """
     When the eventloop of prompt-toolkit is idle, call this inputhook.