Create new port devel/py3-nose:
- This is a variant of devel/py-nose for Python 3.x. A separate port is needed until the ports tree gets VARIANTS support. The science/gramps port will soon be updated to a version which only supports python3, and it depends on py-nose with python3. To allow people to only use packages directly (and not ports), the package building infrastructure needs to build 2 packages: py-nose with python2 and py-nose with python3. Since the ports tree doesn't yet have VARIANTS support, this is not yet possible without making a separate py3-nose port.
- Ensure devel/py-nose does not clobber USES variable in slave devel/py3-nose
- Fix devel/py-nose target regression-test to use selftest.py