dummy_thread/ing: remove in 3.9 (#6408)

https://bugs.python.org/issue37312

stdlib/VERSIONS

@@ -29,8 +29,8 @@ _compression: 3.6-
 _csv: 2.7-
 _curses: 2.7-
 _decimal: 3.6-
-_dummy_thread: 3.6-
-_dummy_threading: 2.7-
+_dummy_thread: 3.6-3.8
+_dummy_threading: 2.7-3.8
 _heapq: 2.7-
 _imp: 3.6-
 _json: 2.7-
@@ -105,7 +105,7 @@ dis: 2.7-
 distutils: 2.7-
 distutils.command.bdist_msi: 2.7-3.10
 doctest: 2.7-
-dummy_threading: 2.7-
+dummy_threading: 2.7-3.8
 email: 2.7-
 encodings: 2.7-
 ensurepip: 2.7-

stubs/six/six/moves/_dummy_thread.pyi

@@ -1 +1,6 @@
-from _dummy_thread import *
+import sys
+
+if sys.version_info >= (3, 9):
+    from _thread import *
+else:
+    from _dummy_thread import *

tests/check_consistent.py

@@ -17,10 +17,7 @@ import re
 
 import tomli
 
-consistent_files = [
-    {"stdlib/@python2/builtins.pyi", "stdlib/@python2/__builtin__.pyi"},
-    {"stdlib/threading.pyi", "stdlib/_dummy_threading.pyi"},
-]
+consistent_files = [{"stdlib/@python2/builtins.pyi", "stdlib/@python2/__builtin__.pyi"}]
 metadata_keys = {"version", "python2", "requires", "extra_description", "obsolete_since"}
 allowed_files = {"README.md"}