Verify and potentially improve Python-related code

- If this package could support installation for multiple versions of Python,
  then please try to adjust the ebuilds to support it.
- Ensure that the ebuilds do not use deprecated functions or variables.
- Please check if Python 3 is supported by this package.
- If this package does not support Python 3:
  - Specify dependency on Python 2.
    You can use PYTHON_DEPEND helper variable, which should be set before
    inheriting of python eclass.
  - If this package cannot support installation for multiple versions of
    Python, then set active version of Python using
    python_set_active_version().
  - Ensure that shebangs in installed scripts specify correct version of
    Python. If shebangs are too generic (e.g. '#!/usr/bin/python'), then you
    can use python_convert_shebangs() to convert shebangs.
    (Wrapper scripts generated by python_generate_wrapper_scripts() do not
    require any changes.)

Please see documentation [1] for more details.
[1] http://www.gentoo.org/proj/en/Python/developersguide.xml

tracked at https://bugs.launchpad.net/gentoo/+bug/634148

Fixed in 4.8.1-r2 and 4.9.0