Bug#940594: Tests fail when applying new upstream commit

I think I sorted it out. While some of the tests interact with $HOME, the sbuild user when autobuilding does not have a real $HOME, but just "/sbuild-nonexistent". So I changed debian/rules as shown in the attached diff. Besides fixing my problem, it allowed me to also enable the ibus-bus

Bug#940594: Tests fail when applying new upstream commit

Package: src:ibus Hello! We are about to upgrade ibus for Ubuntu 19.10 based on ibus 1.5.21-1~exp2. We added the upstream commit since it's a security thing and has also been added to our stable releases.