ansible/ansible — pull request #2037 by blair (2013-02-09 21:10:20+00:00)
Title: PEP-8 fix: always compare with None using 'is' or 'is not'.

http://www.python.org/dev/peps/pep-0008/

Comparisons to singletons like None should always be done with is or
is not, never the equality operators.

Also, beware of writing if x when you really mean if x is not None
-- e.g. when testing whether a variable or argument that defaults to
None was set to some other value. The other value might have a type
(such as a container) that could be false in a boolean context!