Node.traverse() was marked as deprecated since docutils-0.18.  Instead
of it, Node.findall() has been added as successor of traverse().

This applies a patch to docutils-0.17 or older to be available
Node.findall() and use it.

Since 0.18, Element.traverse() returns an iterator instead of
intermediate object.  As a result, the return value is always considered
as truthy value.  And it becomes fragile when the caller modifies the
doctree on the loop.

PropageteDescDomain applies the domain name from the "domain" attribute
of parent node (desc node) to the desc_signature node.  The structure
has longly generated by ObjectDescription.  But it must not be a new
rule.

This allows to build document that contains non standard doctree.