[ANNOUNCE] Tree-Closing Windows May 12, 13

[Dustin Mitchell]

We are planning two tree-closing windows this month, detailed below.  We apologize for the inconvenience, and have taken efforts to plan this work at a minimally disruptive time.  Please get in touch directly with any concerns or questions.

## May 12, 19:30 - 22:30 UTC (12:30 - 3:30 PST)

  * Move Treeherder from Heroku to GCP

  * Backchannel: matrix / #treeherder

## May 13, 12:00 - 16:30 UTC (5am - 9:30am US/Pacific)

  * Pulse RabbitMQ Update - Planned Downtime

    * Backchannel: slack / #pulse

  * Restart network switches attached to CI Mac Minis

  * Restart Mercurial servers to adopt kernel upgrades

Trees will close at 12:00 UTC.  Try pushes can be performed until 14:00 UTC with --closed-tree, but results for those pushes may not be available in a timely fashion.

Dustin