Installation is actually more general than a pg_config interface.

James William Pye · James William Pye · commit 216f194e02b1 · 2009-12-18T14:28:03.000-07:00
Specifically, it is possible for one to be crafted without pg_config.
diff --git a/postgresql/api.py b/postgresql/api.py
@@ -1198,7 +1198,7 @@ class Installation(Element):
 	information about an installation of PostgreSQL accessible by the Python 
 	"""
 	_e_label = "INSTALLATION"
-	_e_factors = ('pg_config_path',)
+	_e_factors = ()
 
 	@propertydoc
 	@abstractproperty
