games-emulation/retroarch: "python" USE Flag Broken

[leycec]

Emerging retroarch with the python USE flag enabled currently fails with the following fatal error:

>>> Emerging (12 of 12) games-emulation/retroarch-9999::abendbrot
 * No Python implementation selected for the build. Please set
 * the PYTHON_SINGLE_TARGET variable in your make.conf to one
 * of the following values:
 * 
 * python3_3 python3_4

 * ERROR: games-emulation/retroarch-9999::abendbrot failed (setup phase):
 *   No supported Python implementation in PYTHON_SINGLE_TARGET/PYTHON_TARGETS.
 * 
 * Call stack:
 *                 ebuild.sh, line  93:  Called pkg_setup
 *     retroarch-9999.ebuild, line  69:  Called python-single-r1_pkg_setup
 *   python-single-r1.eclass, line 446:  Called python_setup
 *   python-single-r1.eclass, line 436:  Called die
 * The specific snippet of code:
 *          die "No supported Python implementation in PYTHON_SINGLE_TARGET/PYTHON_TARGETS."
 * 
 * If you need support, post the output of `emerge --info '=games-emulation/retroarch-9999::abendbrot'`,
 * the complete build log and the output of `emerge -pqv '=games-emulation/retroarch-9999::abendbrot'`.
 * The complete build log is located at '/var/tmp/portage/games-emulation/retroarch-9999/temp/build.log.gz'.
 * The ebuild environment file is located at '/var/tmp/portage/games-emulation/retroarch-9999/temp/die.env'.
 * Working directory: '/usr/lib64/python3.3/site-packages'
 * S: '/var/tmp/portage/games-emulation/retroarch-9999/work/retroarch-9999'

>>> Failed to emerge games-emulation/retroarch-9999, Log file:

>>>  '/var/tmp/portage/games-emulation/retroarch-9999/temp/build.log.gz'

Contrary to the error message, the PYTHON_SINGLE_TARGET variable should never be explicitly set – either in make.conf or package.use. Rather, the ebuild itself should be patched to enable either the python_single_target_python3_3 or python_single_target_python3_4 USE flag (but not both) by default.

Happily, I've fixed this locally and will be submitting a pull request shortly.

[stefan-gr]

Thank you for the patch, will merge your pull request soon.