Guido, thank you for the helpful discussion.  I now think that we should
just add 'end_lineno=None' at the end of the Function/Class __init__
signatures.  pyclbr makes one call to each to contruct the tree it
returns, and the test functions make another call to each.

If those are the only two calls to each, it hardly matters what they
look like.  If there are non-stdlib calls, it is not worth breaking
them. And others might well localize their Function/Class calls within
wrappers similar to _nest_function() and _nest_class().

A more important pyclbr issue, I think, is that readline and readline_ex
return a 'half node', a dict of children, instead of a Module node.  It
is a nuisance, such as when constructing IDLE's module browser tree.  It
is the same as if ast_parse were to return the body list of ast.Module
instead of ast.Module itself.  A readmodule() function could return a
proper tree with a root Module node, with attributes file, name, lineno
(1), end_lineno, and children.