MNT: be cautious about pulling from the bg_cache

tacaswell · tacaswell · commit dd1d72771b0a · 2015-08-26T23:37:01.000-04:00
There are race conditions where _blit_clear may be called before
the first draw (which is what will grab the backgrounds)
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -859,7 +859,11 @@ def _blit_clear(self, artists, bg_cache):
         # cache and restore.
         axes = set(a.axes for a in artists)
         for a in axes:
-            a.figure.canvas.restore_region(bg_cache[a])
+            try:
+                a.figure.canvas.restore_region(bg_cache[a])
+            except KeyError:
+                # something has happened out of order?
+                pass
 
     def _setup_blit(self):
         # Setting up the blit requires: a cache of the background for the
