The B2G bumper bot's last commit was: https://tbpl.mozilla.org/?tree=B2g-Inbound&rev=9ba9a4302268 There have been commits to gaia (and likely others) since, however the bumper bot isn't updating the manifests. Gaia & other B2G trees 'closed' (commit permissions removed) to avoid further pileup.
Revoked access from gaia & b2g-manifest (other repos haven't been touched for days, so leaving it at that for now).
Believed caused by bug 1025788, which I've since reverted - let's see if that helps. A big thanks to pmoore for stepping in to have a look (after the end of his working day), when no-one else was responding in #releng.
The bumper bot has now made another commit: https://tbpl.mozilla.org/?tree=B2g-Inbound&onlyunstarred=1&rev=e99c559f0c4b Though holding off re-opening gaia/b2g-manifests until this goes green, given the pile-up. Bug 1031378 filed for avoiding the bumper bot issues in the future.