Author: Yasushi SHOJI
Revision Date: 2015-10-03 08:24:48 UTC

Handle multiple supported-versions returned by pyversions and py3versions

On Wily with python3-minimal 3.4.3-4ubuntu1,
/usr/share/python3/debian_defaults has multiple version listed in
supported-versions.

 supported-versions = python3.4, python3.5

Those versions return when `py3version -i` is run.

 $ py3versions -i
 python3.4 python3.5

pyversions, with /usr/share/python/debian_defaults, behaves the same.

`pyversions -i` and `py3version -i` is used in snapcraft to generate
PYTHONPATH in Python3ProjectPlugin::python_version(), but due to the
multiple return values separated by a space, it generates the
following PYTHONPATH:

 "....spongeshaker/install/usr/lib/python3.4 python3.5/dist-packages"

and dies with "export: python3.5/dist-packages: bad variable name".

To fix this, just take the first entry of the list. It's usually the
oldest supported version available and safer to rely on.