Merge pull request #1813 from mdboom/gtk3-version-check

GTK segfault with GTK3 and mpl_toolkits

lib/matplotlib/backends/backend_gtk3.py

@@ -3,10 +3,22 @@
 import os, sys
 def fn_name(): return sys._getframe(1).f_code.co_name
 
+try:
+    import gi
+except ImportError:
+    raise ImportError("Gtk3 backend requires pygobject to be installed.")
+
+try:
+    gi.require_version("Gtk", "3.0")
+except ValueError:
+    raise ImportError(
+        "Gtk3 backend requires the GObject introspection bindings for Gtk 3 "
+        "to be installed.")
+
 try:
     from gi.repository import Gtk, Gdk, GObject
 except ImportError:
-    raise ImportError("GTK3 backend requires pygobject to be installed.")
+    raise ImportError("Gtk3 backend requires pygobject to be installed.")
 
 import matplotlib
 from matplotlib._pylab_helpers import Gcf