Lots of similar reports on this (I tried to collect links to all here: S390x Adding APT Sources - No usable temporary directory found - /tmp ENOSPC). I’ve also in the past email Travis support, but no reply, just as there is no reply on this discussion board. They are playing possum… I’d be happy if they at least acknowledged the issue. In the meantime they post a blog post that touts how great their Arm64 support is (see https://blog.travis-ci.com/arm-architecture-adoption-grows-on-travis-ci), when in reality it is full of bugs and apparently unmaintained.