depot_tools: Replace pylint error numbers with symbolic names.

This affects a bunch of files, but only changes comments,
and shouldn't make any difference to behavior.

The purpose is to slightly improve readability of pylint
disable comments.

Change-Id: Ic6cd0f8de792b31d91c6125f6da2616450b30f11
Reviewed-on: https://chromium-review.googlesource.com/420412
Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>
diff --git a/checkout.py b/checkout.py
index 2c59967..4a59000 100644
--- a/checkout.py
+++ b/checkout.py
@@ -414,7 +414,7 @@
     return self.checkout.apply_patch(
         patches, post_processors or self.post_processors, verbose)
 
-  def commit(self, message, user):  # pylint: disable=R0201
+  def commit(self, message, user):  # pylint: disable=no-self-use
     logging.info('Would have committed for %s with message: %s' % (
         user, message))
     return 'FAKE'