rebaseline_server: delete invalid image files from local disk cache

gm/rebaseline_server/imagediffdb.py

 #!/usr/bin/python
 
 """
 Copyright 2013 Google Inc.
 
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 
 Calulate differences between image pairs, and store them in a database.
 """
@@ skipping 369 matching lines @@
   """Wrapper for Image.open(filepath) that yields more useful error messages.
 
   Args:
     filepath: path on local disk to load image from
 
   Returns: a PIL image object
   """
   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
 
 
 def _save_image(image, filepath, format='PNG'):
   """Write an image to disk, creating any intermediate directories as needed.
 
   Args:
     image: a PIL image object
     filepath: path on local disk to write image to
     format: one of the PIL image formats, listed at
@@ skipping 32 matching lines @@
 
   Args:
     expected_image_locator: locator string pointing at expected image
     actual_image_locator: locator string pointing at actual image
 
   Returns: already-sanitized locator where the diffs between expected and
       actual images can be found
   """
   return "%s-vs-%s" % (_sanitize_locator(expected_image_locator),
                        _sanitize_locator(actual_image_locator))