Guido, should we take your comment as approving linking every source, as opposed to only some?  This scope issue is the main sticking point for this issue.  Otherwise, the standard patch is 3 easy new lines after the :synopsis: (and any 'New in Version x.y' note for the module -- see argparse).  The following is Benjamin's patch for #22528.

--- a/Doc/library/pdb.rst
+++ b/Doc/library/pdb.rst
@@ -6,6 +6,9 @@
 .. module:: pdb
    :synopsis: The Python debugger for interactive interpreters.

+**Source code:** :source:`Lib/pdb.py`
+
+--------------

 .. index:: single: debugging
 
Friedrich, were you planning to write a patch, once the list of modules is decided on?  Or should we invite submissions on the core-mentorship list?