Upstream Bodhi 3.0.0 removed support for the USERNAME environment variable due to it clashing with GDM:
This was a backwards incompatible change (in an otherwise backwards incompatble release) since it removed the feature to set usernames with environment variables. Due to this, Bodhi 3.0.0 will not be released on Fedora 26 or 27. However, those Fedora releases are still faced with the issue for GDM users who use a different username on their computer than they do in FAS.
I wrote a devel list post to see what people thought about this, and only got one response:
I'm happy to go with Cole's suggestion, so this update replaces the USERNAME environment variable in F26 and F27 with FAS_USERNAME.
sudo dnf upgrade --advisory=FEDORA-2017-6f382ce708
Please login to add feedback.