PostgresManager fails with custom POSTGRES_EXTRA_DB_BACKEND_BASE

POSTGRES_EXTRA_DB_BACKEND_BASE is documented as a way to use alternative backends but PostgresManager still checks database.ENGINES and fails with Could not locate the 'psqlextra.backend'. django-postgres-extra cannot function without the 'psqlextra.backend'. Looks to be this way in master and 2.0.5.

Or am I using the flag wrong?

django-postgres-extra/psqlextra/manager/manager.py

Lines 22 to 28 in 9aecb3d

    
           has_psqlextra_backend = any( 
        
               [ 
        
                   db_settings 
        
                   for db_settings in settings.DATABASES.values() 
        
                   if "psqlextra" in db_settings["ENGINE"] 
        
               ] 
        
           )

Original issue: #27 . This was 2017 and manager.py was last updated 2 years ago so this could be a regression introduced later.

Oh do I set engine to something like 'psqlextra' and then set POSTGRES_EXTRA_DB_BACKEND_BASE to postgis. I bet that's it...

Yeah that's it.

	has_psqlextra_backend = any(
	[
	db_settings
	for db_settings in settings.DATABASES.values()
	if "psqlextra" in db_settings["ENGINE"]
	]
	)