Simplified test_cursor_var() by using str instead of Database.STRING.

tests/backends/oracle/tests.py

@@ -24,9 +24,8 @@ class Tests(unittest.TestCase):
 
     def test_cursor_var(self):
         """Cursor variables can be passed as query parameters."""
-        from django.db.backends.oracle.base import Database
         with connection.cursor() as cursor:
-            var = cursor.var(Database.STRING)
+            var = cursor.var(str)
             cursor.execute("BEGIN %s := 'X'; END; ", [var])
             self.assertEqual(var.getvalue(), 'X')