bpo-40899: Document exception raised when module cannot be imported

Doc/library/functions.rst

@@ -1968,7 +1968,7 @@ are always available.  They are listed here in alphabetical order.
       This is an advanced function that is not needed in everyday Python
       programming, unlike :func:`importlib.import_module`.
 
-   This function is invoked by the :keyword:`import` statement.  It can be
+   This function is invoked by the :keyword:`import` statement. It can be
    replaced (by importing the :mod:`builtins` module and assigning to
    ``builtins.__import__``) in order to change semantics of the
    :keyword:`!import` statement, but doing so is **strongly** discouraged as it
@@ -2018,6 +2018,9 @@ are always available.  They are listed here in alphabetical order.
    object, the names to import are retrieved and assigned to their respective
    names.
 
+   A :exc:`ImportError` exception can be raised if the module cannot be imported
+   successfully.
+
    If you simply want to import a module (potentially within a package) by name,
    use :func:`importlib.import_module`.
 

Doc/library/importlib.rst

@@ -124,6 +124,9 @@ Functions
     need to call :func:`invalidate_caches` in order for the new module to be
     noticed by the import system.
 
+    A :exc:`ImportError` exception can be raised if the module cannot be imported
+    successfully.
+
     .. versionchanged:: 3.3
        Parent packages are automatically imported.