apache/spark — pull request #1422 by giwa (2014-07-15 22:00:41+00:00)
Title: follow pep8 None should be compared using is or is not

http://legacy.python.org/dev/peps/pep-0008/
## Programming Recommendations
- Comparisons to singletons like None should always be done with is or is not, never the equality operators.