As an FYI, my workaround for this is to grab the squasfh file from https://images.maas.io/ephemeral-v3/daily/bionic/amd64/20190930/ and copy it over the file /var/lib/maas/boot-resources/current/ubuntu/amd64/ga-18.04/bionic/daily/squashfs on my MAAS nodes (assuming you deploy Ubuntu 18.04 with the GA kernel).
As an FYI, my workaround for this is to grab the squasfh file from https:/ /images. maas.io/ ephemeral- v3/daily/ bionic/ amd64/20190930/ and copy it over the file /var/lib/ maas/boot- resources/ current/ ubuntu/ amd64/ga- 18.04/bionic/ daily/squashfs on my MAAS nodes (assuming you deploy Ubuntu 18.04 with the GA kernel).