Fluentd repos are broken on gitter hosts

While updating the package cache on gitter hosts today, all returned the following error

Reading package lists...
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://packages.treasuredata.com trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 901F9177AB97ACBE

W: GPG error: https://deb.nodesource.com trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 1655A0AB68576280
W: Failed to fetch http://packages.treasuredata.com/2/ubuntu/trusty/dists/trusty/InRelease

W: Some index files failed to download. They have been ignored, or old ones used instead.

This is due to an update to the GPG key for fluentd package repositories. We need to download and import the new key (reference the manual process here)

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Some discussion, https://gitlab.slack.com/archives/CB3LSMEJV/p1546890404268400