Be mindful that Synapse can be run alongside other code in the same
Python process. We shouldn't clobber other `SIGHUP` handlers as only one
can be set at time.
(no clobber)
### Background
As part of Element's plan to support a light form of vhosting (virtual
host) (multiple instances of Synapse in the same Python process), we're
currently diving into the details and implications of running multiple
instances of Synapse in the same Python process.
"Per-tenant logging" tracked internally by
https://github.com/element-hq/synapse-small-hosts/issues/48
Relevant to logging as we use a `SIGHUP` to reload log config in
Synapse.
6facf98a3a