Not sure if this is the right component, please move as needed. See for example https://treeherder.mozilla.org/logviewer.html#?job_id=6589442&repo=try - the timestamp at the start of the line is swaddled in ANSI escape sequences, which is fine if the output is directed to a console but probably shouldn't be happening when logging to a file. This seems like a recent regression as I don't recall seeing this before.
It looks like this is specific to taskcluster, and the logging format on that hasn't been fully settled yet: https://bugzilla.mozilla.org/show_bug.cgi?id=1150362 Want to reso:duplicate this one and continue the discussion there?
Sounds good to me.