[1.6.x] Fixed typo and slightly improved error message when db is mis…

…sing time zone definitions.

Refs #21432.

Backport of 32e7580 from master

django/db/models/sql/compiler.py

@@ -1105,8 +1105,8 @@ def results_iter(self):
                 if settings.USE_TZ:
                     if datetime is None:
                         raise ValueError("Database returned an invalid value "
-                                         "in QuerySet.dates(). Are time zone "
-                                         "definitions and pytz installed?")
+                                         "in QuerySet.datetimes(). Are time zone "
+                                         "definitions for your database and pytz installed?")
                     datetime = datetime.replace(tzinfo=None)
                     datetime = timezone.make_aware(datetime, self.query.tzinfo)
                 yield datetime