Synapse on PyPy

fix typo

Limit concurrent event sends for a room

Send federation events concurrently

URL quote path segments over federation

PyPy's incminimark GC can't be triggered manually. From what I observed
there are no obvious issues with just letting it run normally. And
unlike CPython, it actually returns unused RAM to the system.

Signed-off-by: Vincent Breitmoser <look@my.amazin.horse>

For some reason, string interpolation on a DomainSpecificString object
like "%r" % (domainSpecificStringObj) fails under PyPy, because the
default __repr__ implementation wants to iterate over the object. I'm
not sure why that happens, but overriding __repr__ instead of __str__
fixes this problem, and is arguably the more appropriate thing to do
anyways.

The psycopg2 package isn't available for PyPy.  This commit adds a check
if the runtime is PyPy, and if it is uses psycopg2cffi module in favor
of psycopg2. This is almost a drop-in replacement, except for one place
where an additional cast to string is required.

This commit drop-in replaces blist with SortedContainers. They are
written in pure python so work with pypy, but perform as good as
native implementations, at least in a couple benchmarks:

http://www.grantjenks.com/docs/sortedcontainers/performance.html

move handling of auto_join_rooms to RegisterHandler

Add b prefixes to some strings that are bytes in py3

Replace old-style raise with six.reraise

Return 401 for invalid access_token on logout

use python3-compatible prints

Replace some type checks with six type checks

Improve handling of SRV records for federation connections

update prometheus dashboard to use new metric names

Return a 404 rather than a 500 on rejoining empty rooms