It seems that currently you can only use Java7 when you pass a custom property — are there any plans to make this work by default again? https://github.com/technomancy/leiningen/issues/2364

(Should I open an issue?)

Hmm, it looks like fastly (the CDN provider for http://repo.clojars.org) only supports TLS 1.2, so there's not much we can do about it on the clojars side