dev-util/catalyst: drop python-2 support in catalyst-3+

Since python-3 has been stable for years now, it shouldn't be a problem
to start requiring it in this utility.  Let's update the ebuild and see
if anyone complains.

dev-util/catalyst/catalyst-9999.ebuild

@@ -17,7 +17,7 @@ else
 	KEYWORDS="~alpha ~amd64 ~arm ~arm64 ~hppa ~ia64 ~mips ~ppc ~ppc64 ~s390 ~sh ~sparc ~x86 ~x86-fbsd"
 fi
 
-PYTHON_COMPAT=( python{2_7,3_4,3_5} )
+PYTHON_COMPAT=( python{3_4,3_5} )
 
 inherit distutils-r1 multilib ${SRC_ECLASS}