Add black/whitelisting to apply_issue

BUG=370503
TESTS=
apply_issue.py --issue 243483007 --patchset 210001 --whitelst chrome/browser/chromeos/login/screen_locker.cc
apply_issue.py --issue 243483007 --patchset 210001 --blacklist chrome/browser/chromeos/login/screen_locker.cc

Review URL: https://codereview.chromium.org/264823003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@268589 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/checkout.py b/checkout.py
index 022076c..06b2d3b 100644
--- a/checkout.py
+++ b/checkout.py
@@ -726,7 +726,9 @@
         ['diff', base_ref, '--ignore-submodules',
          '--name-only']).splitlines(False)
     assert sorted(patches.filenames) == sorted(found_files), (
-        sorted(patches.filenames), sorted(found_files))
+        'Found extra %s locally, %s not patched' % (
+            sorted(set(found_files) - set(patches.filenames)),
+            sorted(set(patches.filenames) - set(found_files))))
 
   def commit(self, commit_message, user):
     """Commits, updates the commit message and pushes."""