* Raise an exception if there are pending background updates
So we return with a non-0 code
* Changelog
* Port synapse_port_db to async/await
* Port update_database to async/await
* Add version string to mocked homeservers
* Remove unused imports
* Convert overseen bits to async/await
* Fixup logging contexts
* Fix imports
* Add a way to print an error without raising an exception
* Incorporate review
