Python 3 compatibility

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Check what breaks.
What can be done to take advantage of Python 3?

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 http://stackoverflow.com/questions/455717/python-3-development-and-distribution-challenges

Good advice from Mark Hammond who has already had an initial stab at this:

• Change setup.py so it automatically executes the 2to3 tool over the code as 'setup.py install' is run.

• Change almost all literal strings to become 'byte strings' in a 2 and 3 compatible way. The simplest way to do this was to use (say) "foo".encode("ascii") - in that case the literal string "foo" becomes a str object on py2k and a bytes object on py3k, and given all literals are ascii chars, the hard-coding of 'ascii' is reasonable.

• A few other misc conversions between bytes and strings.

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Consider using something like tox to test with different Python versions.

 http://codespeak.net/tox

[menno]

Document how Python3 support and testing works (eg. tox).