DocTestFinder._find():  for tests derived from a module __test__ global,
doctest always promised to stick "__test__" in the name.  That got
broken.  Now it's fixed again.
diff --git a/Lib/doctest.py b/Lib/doctest.py
index 3a8496f..2aa7408 100644
--- a/Lib/doctest.py
+++ b/Lib/doctest.py
@@ -1019,7 +1019,7 @@
                                      "must be strings, functions, methods, "
                                      "classes, or modules: %r" %
                                      (type(val),))
-                valname = '%s.%s' % (name, valname)
+                valname = '%s.__test__.%s' % (name, valname)
                 self._find(tests, val, valname, module, source_lines,
                            globs, seen)