Document the import semantics that if None is found in sys.modules for a module then ImportError is raised.

brettcannon · brettcannon · commit 757df6e4cd05 · 2009-08-30T04:00:12.000Z
diff --git a/Doc/reference/simple_stmts.rst b/Doc/reference/simple_stmts.rst
@@ -668,7 +668,9 @@ Once the name of the module is known (unless otherwise specified, the term
 "module" will refer to both packages and modules), searching
 for the module or package can begin. The first place checked is
 :data:`sys.modules`, the cache of all modules that have been imported
-previously. If the module is found there then it is used in step (2) of import.
+previously. If the module is found there then it is used in step (2) of import
+unless :keyword:`None` is found in :data:`sys.modules`, in which case
+:exc:`ImportError` is raised.
 
 .. index::
     single: sys.meta_path
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -174,6 +174,9 @@ Build
 Documenation
 ------------
 
+- Document that importing a module that has None in sys.modules triggers an
+  ImportError.
+
 - Issue #6556: Fixed the Distutils configuration files location explanation
   for Windows.
 
