Don't throw "line too long" presubmit error on python import statements or when pylint "line too long" is disabled.

BUG=

Review URL: https://codereview.chromium.org/1234333002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@296035 0039d316-1c4b-4281-b951-d872f2087c98