Per the discussion in the comments on [this commit](https://github.com/apache/spark/commit/f17d43b033d928dbc46aef8e367aa08902e698ad#commitcomment-10780649), this PR allows the Python lint script to reuse `pep8.py` when possible.

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #5561 from nchammas/save-dem-pep8-bytes and squashes the following commits:

b7c91e6 [Nicholas Chammas] reuse pep8.py