More py3 compat

[leifj]

All Submissions:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you added an explanation of what problem you are trying to solve with this PR?
• Have you added information on what your changes do and why you chose this as your solution?
• Have you written new tests for your changes?
• [x ] Does your submission pass tests?
• This project follows PEP8 style guide. Have you run your code against the 'flake8' linter?

[coveralls]

Coverage increased (+0.07%) to 73.254% when pulling a2151d2 on more-py3-compat into d724f8d on master.

[johanlundberg]

codecs in p11_test.py is an unused import statement