Updated dev Python scripts to make them PEP8 compliant.

Author: Reynold Xin <rxin@apache.org>

Closes #875 from rxin/pep8-dev-scripts and squashes the following commits:

04b084f [Reynold Xin] Made dev Python scripts PEP8 compliant.

(cherry picked from commit 9ed37190f45fd9e6aa0f2c73b66d317732a53eb8)
Signed-off-by: Reynold Xin <rxin@apache.org>