Add support for empty files, __init__.py is a common example.

rietveld.py

 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """Defines class Rietveld to easily access a rietveld instance.
 
 Security implications:
 
 The following hypothesis are made:
 - Rietveld enforces:
   - Nobody else than issue owner can upload a patch set
@@ skipping 124 matching lines @@
         # safe to use.
         # props = state.get('property_changes', '').splitlines() or []
         props = []
         if state['is_binary']:
           out.append(patch.FilePatchBinary(
               filename,
               self.get_file_content(issue, patchset, state['id']),
               props,
               is_new=(status[0] == 'A')))
         else:
-          if state['num_chunks']:
+          # Ignores num_chunks since it may only contain an header.
+          try:
             diff = self.get_file_diff(issue, patchset, state['id'])
-          else:
-            raise patch.UnsupportedPatchFormat(
-                filename, 'File doesn\'t have a diff.')
+          except urllib2.HTTPError, e:
+            if e.code == 404:
+              raise patch.UnsupportedPatchFormat(
+                  filename, 'File doesn\'t have a diff.')
           out.append(patch.FilePatchDiff(filename, diff, props))
+          if status[0] == 'A':
+            # It won't be set for empty file.
+            out[-1].is_new = True
       else:
         # Line too long (N/80)
         # pylint: disable=C0301
         # TODO: Add support for MM, A+, etc. Rietveld removes the svn properties
         # from the diff.
         # Example of mergeinfo across branches:
         # http://codereview.chromium.org/202046/diff/1/third_party/libxml/xmlcatalog_dummy.cc
         # svn:eol-style property that is lost in the diff
         # http://codereview.chromium.org/202046/diff/1/third_party/libxml/xmllint_dummy.cc
         # Change with no diff, only svn property change:
@@ skipping 50 matching lines @@
         if retry >= (maxtries - 1):
           raise
         if not 'Name or service not known' in e.reason:
           # Usually internal GAE flakiness.
           raise
       # If reaching this line, loop again. Uses a small backoff.
       time.sleep(1+maxtries*2)
 
   # DEPRECATED.
   Send = get