Clarify importlib.machinery.PathFinder's difference from what __import__() does.

diff --git a/Doc/library/importlib.rst b/Doc/library/importlib.rst
index 66a5c4e6052abd2063f6e11ff72f9eeceee2d29b..e5cc27f974a46cd8ee53f80db0c30cf6afdcaf8f 100644 (file)
--- a/Doc/library/importlib.rst
+++ b/Doc/library/importlib.rst
@@ -477,7 +477,9 @@ find and load modules.
 
     This class does not perfectly mirror the semantics of :keyword:`import` in
     terms of :data:`sys.path`. No implicit path hooks are assumed for
-    simplification of the class and its semantics.
+    simplification of the class and its semantics. This implies that when
+    ``None`` is found in :data:`sys.path_importer_cache` that it is simply
+    ignored instead of implying a default finder.
 
     Only class methods are defined by this class to alleviate the need for
     instantiation.