Updated docs after changing select_for_update() to raise NotSupportedError.

Follow up to 054a44d6.

docs/ref/databases.txt

@@ -569,7 +569,8 @@ Row locking with ``QuerySet.select_for_update()``
 
 MySQL does not support the ``NOWAIT`` and ``SKIP LOCKED`` options to the
 ``SELECT ... FOR UPDATE`` statement. If ``select_for_update()`` is used with
-``nowait=True`` or ``skip_locked=True`` then a ``DatabaseError`` will be raised.
+``nowait=True`` or ``skip_locked=True``, then a
+:exc:`~django.db.NotSupportedError` is raised.
 
 Automatic typecasting can cause unexpected results
 --------------------------------------------------

docs/ref/models/querysets.txt

@@ -1640,8 +1640,8 @@ backends support ``select_for_update()``. However, MySQL doesn't support the
 ``nowait`` and ``skip_locked`` arguments.
 
 Passing ``nowait=True`` or ``skip_locked=True`` to ``select_for_update()``
-using database backends that do not support these options, such as MySQL, will
-cause a :exc:`~django.db.DatabaseError` to be raised. This prevents code from
+using database backends that do not support these options, such as MySQL,
+raises a :exc:`~django.db.NotSupportedError`. This prevents code from
 unexpectedly blocking.
 
 Evaluating a queryset with ``select_for_update()`` in autocommit mode on

tests/select_for_update/tests.py

@@ -134,7 +134,7 @@ class SelectForUpdateTests(TransactionTestCase):
     @skipUnlessDBFeature('has_select_for_update')
     def test_unsupported_nowait_raises_error(self):
         """
-        DatabaseError is raised if a SELECT...FOR UPDATE NOWAIT is run on
+        NotSupportedError is raised if a SELECT...FOR UPDATE NOWAIT is run on
         a database backend that supports FOR UPDATE but not NOWAIT.
         """
         with self.assertRaisesMessage(NotSupportedError, 'NOWAIT is not supported on this database backend.'):
@@ -145,8 +145,8 @@ class SelectForUpdateTests(TransactionTestCase):
     @skipUnlessDBFeature('has_select_for_update')
     def test_unsupported_skip_locked_raises_error(self):
         """
-        DatabaseError is raised if a SELECT...FOR UPDATE SKIP LOCKED is run on
-        a database backend that supports FOR UPDATE but not SKIP LOCKED.
+        NotSupportedError is raised if a SELECT...FOR UPDATE SKIP LOCKED is run
+        on a database backend that supports FOR UPDATE but not SKIP LOCKED.
         """
         with self.assertRaisesMessage(NotSupportedError, 'SKIP LOCKED is not supported on this database backend.'):
             with transaction.atomic():
@@ -189,7 +189,7 @@ class SelectForUpdateTests(TransactionTestCase):
 
     @skipIfDBFeature('supports_select_for_update_with_limit')
     def test_unsupported_select_for_update_with_limit(self):
-        msg = 'LIMIT/OFFSET not supported with select_for_update on this database backend.'
+        msg = 'LIMIT/OFFSET is not supported with select_for_update on this database backend.'
         with self.assertRaisesMessage(NotSupportedError, msg):
             with transaction.atomic():
                 list(Person.objects.all().order_by('pk').select_for_update()[1:2])