Fix pylint check in presubmit

This fixes the unexpected behavior where we only run pylint over the
affected Python files *unless* there are affected Python files which we
have explicitly blacklisted, in which case we run pylint over ALL Python
files in every subdirectory of the Skia checkout, including repos in
DEPS.

- Added buildtools and common to the blacklist.
- Changed to run pylint over all Python files in Skia, like
  presubmit_support expects.
- Fix existing pylint problems.

Bug: skia:
Change-Id: Ife1321f5ae5eaff2a28cc14c99a82a0716c12677
Reviewed-on: https://skia-review.googlesource.com/137126
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Eric Boren <borenet@google.com>

0 files changed, 0 insertions, 0 deletions