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

We aren't ready to release this yet, so I'm reverting it for now.

This reverts commit d1679a4e, reversing
changes made to e089100c.

Filter ourselves out of the server list before checking for an empty remote
host list, to fix 500 error

Fixes #2141

Signed-off-by: Adrian Tschira <nota@notafile.com>

The old style raise is invalid syntax in python3. As noted in the docs,
this adds one more frame in the traceback, but I think this is
acceptable:

    <ipython-input-7-bcc5cba3de3f> in <module>()
         16     except:
         17         pass
    ---> 18     six.reraise(*x)

    /usr/lib/python3.6/site-packages/six.py in reraise(tp, value, tb)
        691             if value.__traceback__ is not tb:
        692                 raise value.with_traceback(tb)
    --> 693             raise value
        694         finally:
        695             value = None

    <ipython-input-7-bcc5cba3de3f> in <module>()
          9
         10 try:
    ---> 11     x()
         12 except:
         13     x = sys.exc_info()

Also note that this uses six, which is not formally a dependency yet,
but is included indirectly since most packages depend on it.

Signed-off-by: Adrian Tschira <nota@notafile.com>

Implement group join API

Add response size metrics

postgres port script: fix state_groups_pkey error

as opposed to join_policy, which is really only pertinent to the
synapse implementation of the group server.

By doing this we keep the group server concept extensible by
allowing arbitrarily complex rules for deciding whether a group
is openly joinable.

Fixes https://github.com/matrix-org/synapse/issues/3050.

Improve logging and comments. Group all the stuff to do with inspecting tables
together rather than creating the port tables in the middle.

We really shouldn't spit out "Failed to create port table", it looks scary.

use PUT instead of POST for federating groups/m.join_policy