Requiring hostname for postgresql doesn't work with socket based connections

[adamgreig]

Bug Report

Describe the bug

I'm using Django with PostgreSQL on the same server, and so it connects using a UNIX socket and IDENT authentication - the only configuration required is the database name, there's no hostname or username. However, create_postgres_uri() requires that host is set:

django-dbbackup/dbbackup/db/postgresql.py

Lines 10 to 13 in 790ec8b

	def create_postgres_uri(self):
	host = self.settings.get("HOST")
	if not host:
	raise DumpError("A host name is required")

The correct URI to generate is just postgresql:///dbname, which would be generated correctly without this check, and works fine with pg_dump. As far as I can tell, it would be enough to just remove this check, and if connection later fails, pg_dump's error can be reported instead. I'm happy to open a PR if that sounds like an acceptable solution.

[stribny]

I just run into this problem, so +1 and would be great to have this fix!