These are needed for a future feature where tools migrated to
Kubernetes are removed from the listing.

Bug: T280037

Bug: T215588

Add a nag.py script that can be used to send notification emails to
maintainers of tools that have been seen to run jobs on the Trusty grid
in the last 7 days.

Drill down views are probably more useful than links to contact
information for most users.

Try again to get the logic right for a recursion guard when expanding
tool membership. The prior logic incorrectly kept a single tracking list
across all tools. There could be further optimization here using
memoization, but hopefully we can get by without that.

Follow up to 995ce794 where I was apparently unable to read the code.

When collecting the list of members for a given tool, recursively expand
any tools that are found.

Python3's dict.keys() method iterates on the live dict instead of
returning a copy of the keys.

A lot of the data collection logic can be replaced by calling existing
webservices with json apis.

No official deadline yet, but there is a draft announce page on wikitech
to link to.

This reverts commit 3e9aaa27.