Issue #15767: Add ModuleNotFoundError.
diff --git a/Doc/c-api/exceptions.rst b/Doc/c-api/exceptions.rst
index 226b619..5644410 100644
--- a/Doc/c-api/exceptions.rst
+++ b/Doc/c-api/exceptions.rst
@@ -782,6 +782,8 @@
 +-----------------------------------------+---------------------------------+----------+
 | :c:data:`PyExc_ImportError`             | :exc:`ImportError`              |          |
 +-----------------------------------------+---------------------------------+----------+
+| :c:data:`PyExc_ModuleNotFoundError`     | :exc:`ModuleNotFoundError`      |          |
++-----------------------------------------+---------------------------------+----------+
 | :c:data:`PyExc_IndexError`              | :exc:`IndexError`               |          |
 +-----------------------------------------+---------------------------------+----------+
 | :c:data:`PyExc_InterruptedError`        | :exc:`InterruptedError`         |          |
diff --git a/Doc/library/exceptions.rst b/Doc/library/exceptions.rst
index 1747efe..a428f51 100644
--- a/Doc/library/exceptions.rst
+++ b/Doc/library/exceptions.rst
@@ -170,8 +170,9 @@
 
 .. exception:: ImportError
 
-   Raised when an :keyword:`import` statement fails to find the module definition
-   or when a ``from ... import`` fails to find a name that is to be imported.
+   Raised when the :keyword:`import` statement has troubles trying to
+   load a module.  Also raised when the "from list" in ``from ... import``
+   has a name that cannot be found.
 
    The :attr:`name` and :attr:`path` attributes can be set using keyword-only
    arguments to the constructor. When set they represent the name of the module
@@ -181,6 +182,14 @@
    .. versionchanged:: 3.3
       Added the :attr:`name` and :attr:`path` attributes.
 
+.. exception:: ModuleNotFoundError
+
+   A subclass of :exc:`ImportError` which is raised by :keyword:`import`
+   when a module could not be located.  It is also raised when ``None``
+   is found in :data:`sys.modules`.
+
+   .. versionadded:: 3.6
+
 
 .. exception:: IndexError