unsupported string prefix in 2.4

http://docs.python.org/release/2.4/ref/strings.html
This is also ignored on later version of python 2
and is present only for python 3 conversion, as seen
on http://docs.python.org/2/reference/lexical_analysis.html#string-literals

Also see http://stackoverflow.com/questions/6269765/what-does-the-b-character-do-in-front-of-a-string-literal

Fix https://github.com/ansible/ansible/issues/4739