Prior to synapseclient 2.0.0 one could
to change the synapse cache location. In 2.0.0 the cache module was moved under core, and while setting the value under core works, we don't want people looking under core as the point of it was to signal that that wasn't public and was subject to change across releases. So we should have a supported way of setting this value now, as it's necessary in e.g. a lambda environment or somewhere else where the home directory is not a useful default.