Python3 lowpass changes, zero impact to Python 2.6+

[lathama]

#147 broken apart with just the simple Python3 changes.

1. setup.py will display the error now vs just failing
2. exception splitting in dhcp.py works across Python versions
3. file open changes, using io.open works across Python versions
4. Print is a function, no future import needed. https://docs.python.org/2.6/library/functions.html#print

Disclaimer, I did the proof of concept for Ansible and Python3, not my first roller coaster.

will note the getuid vs geteuid in another PR

[psychomario]

👍