rebaseline_server: delete invalid image files from local disk cache

gm/rebaseline_server/imagediffdb.py

Index: gm/rebaseline_server/imagediffdb.py
diff --git a/gm/rebaseline_server/imagediffdb.py b/gm/rebaseline_server/imagediffdb.py
index a53eb1fb96d1c704fe9410be2bfbe8b22c54864a..8328543c935d77bbdc011701d85356c78fe9270f 100644
--- a/gm/rebaseline_server/imagediffdb.py
+++ b/gm/rebaseline_server/imagediffdb.py
@@ -387,7 +387,10 @@ def _open_image(filepath):
   try:
     return Image.open(filepath)
   except IOError:
-    logging.error('IOError loading image file %s' % filepath)
+    # If we are unable to load an image from the file, delete it from disk
+    # and we will try to fetch it again next time.  Fixes http://skbug.com/2247
+    logging.error('IOError loading image file %s ; deleting it.' % filepath)
+    os.remove(filepath)

[borenet, 2014/03/26 13:17:21]

Is there a chance that the file may not exist?  I guess we don't care too much
if os.remove raises an exception, since we're about to raise IOError anyway.

[epoger, 2014/03/26 13:38:12]

I suppose it's possible.  For the reason you mention, I figured I would just
keep the change as simple as possible.

     raise