Handle HttpResponseException when using federation client.

Fix email notifications for unnamed rooms with multiple people

Only start background group attestation renewals on master

Including workers!

Fix 3PID invite room state over federation.

Allow server admins to define implementations of extra rules for allowing or denying incoming events

Prometheus histograms are cumalative

Fix background job for deactivated flag

Fixes that when a user exchanges a 3PID invite for a proper invite over
federation it does not include the `invite_room_state` key.

This was due to synapse incorrectly sending out two invite requests.

Don't send renewal emails to deactivated users (second attempt)

Use python3 in the demo

Don't log exception when failing to fetch remote content.

Fix Prometheus erroring after the extremities monitoring

because this file is reproduced on dockerhub and relative paths don't work

* py3 fixes for federation_client
* .well-known support for federation_client

This code confused the hell out of me today. Split _get_new_device_messages
into its two (unrelated) parts.

* remove 2.7 from CI and publishing

* fill out classifiers and also make it not be installed on 3.5

* some minor bumps so that the old deps work on python 3.5

Change password reset links to /_matrix.

Add FAQ questions to federate.md. Add a health warning making it clear that the 1711 upgrade FAQ is now out of date.