I am also seeing disk quota exceeded but on ppc64le. I have added df commands these but shows plenty of space.
Here are some examples:
https://travis-ci.org/github/djlwilder/ovs/jobs/669791873
https://travis-ci.org/github/djlwilder/ovs/jobs/668945838
https://travis-ci.org/github/djlwilder/dpdk/builds/669007111
These builds run ARM64, X86 and ppc64le jobs, I am only seeing the problem on ppc64le builds.
Thanks