Change RunPylint to parse all .py files when one is modified.

Make all depot_tools/tests pass on pylint. That mostly meant fixing some
builtins aliasing, wrong alignment and turning off most remaining warnings.

BUG=none
TEST=unit tests

Review URL: http://codereview.chromium.org/5695007

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@69159 0039d316-1c4b-4281-b951-d872f2087c98