Implement PEP 451 (ModuleSpec).
diff --git a/Lib/importlib/machinery.py b/Lib/importlib/machinery.py
index ff826e4..2e1b2d7 100644
--- a/Lib/importlib/machinery.py
+++ b/Lib/importlib/machinery.py
@@ -5,6 +5,7 @@
 from ._bootstrap import (SOURCE_SUFFIXES, DEBUG_BYTECODE_SUFFIXES,
                          OPTIMIZED_BYTECODE_SUFFIXES, BYTECODE_SUFFIXES,
                          EXTENSION_SUFFIXES)
+from ._bootstrap import ModuleSpec
 from ._bootstrap import BuiltinImporter
 from ._bootstrap import FrozenImporter
 from ._bootstrap import WindowsRegistryFinder