dev-python/python-caja is missing PYTHON_COMPAT higher than python2_7 This should be tracked by Python3.6 switch Tracker: https://bugs.gentoo.org/656406 However, with Mate-1.20 from an overlay and changing PYTHON_COMPAT in the ebuild: < PYTHON_COMPAT=( python2_7 ) --- > PYTHON_COMPAT=( python3_6 ) python-caja emerges using "/usr/lib64/libpython3.6.so.1.0" in /usr/lib64/caja/extensions-2.0/libcaja-python.so But I have not tested yet running it!
It would appear that python 3 support has been tagged for 1.22 release. https://github.com/mate-desktop/python-caja/issues/30 As far as I can tell, nothing actually uses python-caja in mate, unless you explicitly install it.
it doesn't affect the switch as it has no previous python3 in PYTHON_COMPAT
Pardon me. I thought the tracker bug is about to get rid of python-2
Gentoo is trying to change python 3 from 3.5 to 3.6. Python 2.7 is still the default python 2 implementation and is being supported by upstream until 2020. Unless mate updates python-caja to support Python 3 (and preferably 3.6 in this case) I don't believe there is anything for me to do here. Sorry.