replaced e.message

BaseException.message has been deprecated as of Python 2.6.

http://legacy.python.org/dev/peps/pep-0352/

Replaced e.message with six.text_type(e) (uses unicode with
Python 2.x and str with Python 3.x).

Change-Id: I8d0c43f9383cec343ca159061b7a93d3db45a74a