Failing tests due to missing /dev/pts (?) mount

I packaged umockdev for mir in the feature/unity8 branch. It had some Musl problems but upstream helped us out really well and now even has it's CI set to test it in the future!

Right now the only thing left is a few failing tests, which according to a comment by the developer, might be due to a missing /dev/pts mount (or wrong permissions). Could we maybe just add the mount to the packaging chroot?