[gpsd-dev] Python 3 Updates

[Fred Wright]

I now have Python 3 support fully usable, though there's still some
cleanup to do (e.g. a division audit).  I've been pushing commits to my
GitHub all along, but since there doesn't seem to be much interest in
pulling from there, I'll send the patches (12 so far) here.

Short-form summary (forward chronological):

MacPro:gpsd fw$ git log --oneline --reverse master...python3
7e3a674 Fixes Python C extensions for Python 3 compatibility.
c35b535 Fixes fake.py 'packet' import for Python 3.
e85b05e Forces Python 3 import behavior in all gps/* modules.
070b5f6 Fixes xgps for Python 3.
ad32677 Fixes a client.py exception for Python 3.
2a48a82 Fixes Gtk warnings related to xgps/xgpsspeed error boxes.
b0dcaa3 Changes type checks in misc.py:isotime to use isinstance().
2f81162 Removes unnecessary Unicode literal from xgps.
711fd3c Fixes gpscat and test_maidenhead.py for Python 3.
9bbfb2c Fixes fake.py and gpsfake for Python 3.
8dc7809 Adds "target Python" support to SConstruct.
c7dbc29 Removes redundant polystr/polybytes defs from client.py.

Also viewable here:

https://github.com/fhgwright/gpsd/compare/master...python3

Note that, at least in the MacPorts case, the C extensions built for 3.5
use versioned naming and hence don't work for any other version, including
3.x, while builds for other 3.x versions work with all 3.x versions.
OTOH, that makes it possible for 2.x and 3.5 extensions to coexist.  None
of this matters for *installed* libraries, though, which live in a
version-specific directory in all cases.

The default behavior is still to build for the scons Python (usually 2.7
and never 3.x for now).

Fred Wright