Invoke import on importlib.machinery directly. Access an attribute to force...

Invoke import on importlib.machinery directly. Access an attribute to force import in delayed-import environments. Fixes #487.

CHANGES.txt

@@ -2,6 +2,13 @@
 CHANGES
 =======
 
+19.4.1
+------
+
+* Issue #487: Use direct invocation of ``importlib.machinery``
+  in ``pkg_resources`` to avoid missing detection on relevant
+  platforms.
+
 19.4
 ----
 

pkg_resources/__init__.py

@@ -60,10 +60,11 @@ except ImportError:
 from os import open as os_open
 from os.path import isdir, split
 
-# Avoid try/except due to potential problems with delayed import mechanisms.
-if sys.version_info >= (3, 3) and sys.implementation.name == "cpython":
+try:
     import importlib.machinery as importlib_machinery
-else:
+    # access attribute to force import under delayed import mechanisms.
+    importlib_machinery.__name__
+except ImportError:
     importlib_machinery = None
 
 try: