Do not require GTK to be either present or usable to start.

Before, we only checked that we could import GTK, but in a linux
console, it's possible to import it while not being able to start it
(no X11 present).

This should resolve https://bugzilla.redhat.com/show_bug.cgi?id=646079
Thanks to Tom Spura for reporting it.

IPython/Shell.py

@@ -1152,7 +1152,8 b' class IPShellMatplotlibQt4(IPShellQt4):'
 def check_gtk(mode):
     try:
         import gtk
-    except ImportError:
+    except (ImportError, RuntimeError):
+        # GTK not present, or can't be started (no X11, happens in console)
         return mode
     if hasattr(gtk,'set_interactive'):
         gtk.set_interactive(False)
@@ -1243,6 +1244,7 b' def _select_shell(argv):'
             th_mode = 'tkthread'
 
         # New versions of pygtk don't need the brittle threaded support.
+        if th_mode == 'gthread':
         th_mode = check_gtk(th_mode)
         return th_shell[th_mode]