The latest version of Jinja 2 chose to disable speedups by default (which is a bit sad). These can be enabled at compile time which my soon to be attached patch does. Gentoo has always built these speedups – I don't see a reason to skip them.
Created attachment 204109 [details, diff] Enable speedups
Also, tests require dev-python/nose ;)
Fixed in dev-python/jinja2-2.2.1.