'xml:' namespace causes lxml treebuilder crash

[Leonard Richardson]

The "xml:" namespace is bound by definition to the namespace URL "http://www.w3.org/XML/1998/namespace". But the lxml tree builder doesn't know this.

When lxml finds a tag with an "xml:" attribute, it tells the tree builder that the tag's namespace is "http://www.w3.org/XML/1998/namespace". The tree builder can't find this namespace in its mapping, so it says the namespace is None, which causes a crash.

Problematic document:

<a xml:lang="foo">bar</a>

[Leonard Richardson (leonardr)]

Fixed in revision 266.