made username lookup work with psycopg 3

src/core/tests/runner.py

@@ -2,11 +2,18 @@ from types import MethodType
 from django.test.runner import DiscoverRunner
 from django.db import connections
 
+
 def prepare_database(self):
     self.connect()
+
+    try:
+        username = self.connection.get_dsn_parameters()['user']
+    except AttributeError:  # psycopg has moved this method
+        username = self.connection.info.get_parameters()['user']
+
     self.connection.cursor().execute(f"""
-    CREATE SCHEMA rc3schema AUTHORIZATION {self.connection.get_dsn_parameters()["user"]};
-    GRANT ALL ON SCHEMA rc3schema TO {self.connection.get_dsn_parameters()["user"]};
+    CREATE SCHEMA rc3schema AUTHORIZATION {username};
+    GRANT ALL ON SCHEMA rc3schema TO {username};
     """)