Throw an exception if MPLBACKEND is invalid.

anntzer · anntzer · commit 6125d81347e1 · 2016-07-12T00:28:16.000-07:00
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -1460,7 +1460,7 @@ def tk_window_focus():
     # variable MPLBACKEND
     try:
         use(os.environ['MPLBACKEND'])
-    except (KeyError, ValueError):
+    except KeyError:
         pass
 
 
