roll_deps: Return a tuple even when returning early

tools/roll_deps.py

 #!/usr/bin/python2
 
 # Copyright 2014 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Skia's Chromium DEPS roll script.
 
 This script:
@@ skipping 398 matching lines @@
     git = config.git
     with misc_utils.ChangeDir(config.chromium_path, config.verbose):
         config.vsp.check_call([git, 'fetch', '-q', 'origin'])
 
         old_revision = misc_utils.ReSearch.search_within_output(
             config.verbose, '"skia_revision": "(?P<return>[0-9]+)",', None,
             [git, 'show', 'origin/master:DEPS'])
         assert old_revision
         if revision == int(old_revision):
             print 'DEPS is up to date!'
-            return None
+            return (None, None)
 
         master_hash = config.vsp.strip_output(
             [git, 'show-ref', 'origin/master', '--hash'])
         master_revision = get_svn_revision(config, 'origin/master')
 
         # master_hash[8] gives each whitespace CL a unique name.
         if config.save_branches:
             branch = 'control_%s' % master_hash[:8]
         else:
             branch = None
@@ skipping 69 matching lines @@
     if partial_hash:
         revision, git_hash = revision_and_hash_from_partial(
             config, partial_hash)
     elif revision:
         revision, git_hash = revision_and_hash_from_revision(config, revision)
     else:
         revision, git_hash = revision_and_hash(config)
 
     print 'revision=%r\nhash=%r\n' % (revision, git_hash)
 
-    roll = roll_deps(config, revision, git_hash)
+    deps_issue, whitespace_issue = roll_deps(config, revision, git_hash)
 
-    if roll:
-        deps_issue, whitespace_issue = roll
+    if deps_issue and whitespace_issue:
         print 'DEPS roll:\n    %s\n' % deps_issue
         print 'Whitespace change:\n    %s\n' % whitespace_issue
+    else:
+        print >> sys.stderr, 'No issues created.'
 
 
 def main(args):
     """main function; see module-level docstring and GetOptionParser help.
 
     Args:
         args: sys.argv[1:]-type argument list.
     """
     option_parser = DepsRollConfig.GetOptionParser()
     options = option_parser.parse_args(args)[0]
 
     if not options.chromium_path:
         option_parser.error('Must specify chromium_path.')
     if not os.path.isdir(options.chromium_path):
         option_parser.error('chromium_path must be a directory.')
 
     if not git_utils.git_executable():
         option_parser.error('Invalid git executable.')
 
     config = DepsRollConfig(options)
     find_hash_and_roll_deps(config, options.revision, options.git_hash)
 
 
 if __name__ == '__main__':
     main(sys.argv[1:])