Merge branch 'feature/make-2.6-compatible' into 'releases/2.6'

Patch releases/2.6 branch to work with 2.6 releases

See merge request !178
5 jobs for v2.6.0 in 11 minutes and 5 seconds (queued for 1 second)
latest
Status Name Job ID Coverage
  Test
passed debian:10 gcc:c++17 #42034
duneci

00:11:05

passed debian:9--clang #42036
duneci

00:08:26

passed debian:9--gcc #42035
duneci

00:08:29

passed ubuntu:16.04--clang #42038
duneci

00:08:25

passed ubuntu:16.04--gcc #42037
duneci

00:04:32