bpo-30262: Don't expose private objects in sqlite3 (GH-1440)

The Cache and Statement objects are undocumented and implementation
details of the sqlite3 module.

They aren't usable from pure Python code.

Doc/whatsnew/3.8.rst

@@ -796,6 +796,10 @@ The following features and APIs have been removed from Python 3.8:
 * "unicode_internal" codec is removed.
   (Contributed by Inada Naoki in :issue:`36297`.)
 
+* The ``Cache`` and ``Statement`` objects of the :mod:`sqlite3` module are not
+  exposed to the user.
+  (Contributed by Aviv Palivoda in :issue:`30262`.)
+
 
 Porting to Python 3.8
 =====================

Misc/NEWS.d/next/Library/2019-05-09-12-38-40.bpo-30262.Tu74ak.rst

+The ``Cache`` and ``Statement`` objects of the :mod:`sqlite3` module are not
+exposed to the user.  Patch by Aviv Palivoda.

Modules/_sqlite/module.c

@@ -366,10 +366,6 @@ PyMODINIT_FUNC PyInit__sqlite3(void)
     PyModule_AddObject(module, "Connection", (PyObject*) &pysqlite_ConnectionType);
     Py_INCREF(&pysqlite_CursorType);
     PyModule_AddObject(module, "Cursor", (PyObject*) &pysqlite_CursorType);
-    Py_INCREF(&pysqlite_CacheType);
-    PyModule_AddObject(module, "Statement", (PyObject*)&pysqlite_StatementType);
-    Py_INCREF(&pysqlite_StatementType);
-    PyModule_AddObject(module, "Cache", (PyObject*) &pysqlite_CacheType);
     Py_INCREF(&pysqlite_PrepareProtocolType);
     PyModule_AddObject(module, "PrepareProtocol", (PyObject*) &pysqlite_PrepareProtocolType);
     Py_INCREF(&pysqlite_RowType);