I cracked, and added some type definitions in synapse.storage.

Ensure good comprehension hygiene using flake8-comprehensions.

Add typing information to the spam checker modules.

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

This looks like it got half-killed back in #888.

Fixes #6567.

... and update INSTALL.md to include py3.8.

We'll also have to update the buildkite pipeline to run it

* update version of black and also fix the mypy config being overridden

Add a linting script that enforces all boolean values in the default config be lowercase.

This has annoyed me for a while so I decided to fix it.

* Fix presence timeouts when synchrotron restarts.

Handling timeouts would fail if there was an external process that had
timed out, e.g. a synchrotron restarting. This was due to a couple of
variable name typoes.

Fixes #3715.

* 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

* Pin eliot to <1.8 on python 3.5.2

Fixes https://github.com/matrix-org/synapse/issues/5199

* Add support for 'markers' to python_dependencies

* tell xargs not to strip quotes

pip 19.1 otherwise complains about "editable mode is not supported for
pyproject.toml-style projects"

* Run unit tests against python 3.7

... so that we span the full range of our supported python versions

* Switch to xenial

* fix psql fail

* pep8 etc want python 3.6