Avoid class reference to imported function
Avoid class reference to imported function

We import the urljoin() function directly to support both Py2 and Py3, so the
reference to urlparse.urljoin() raises an exception. Don't do that!

Fixes 574.

Signed-off-by: Dan Scott <2591e5f46f28d303f9dc027d475a5c60d8dea17a@coffeecode.net>

RDFLib/rdflib,dbs/rdflib,dbs/rdflib,RDFLib/rdflib,dbs/rdflib,RDFLib/rdflib,RDFLib/rdflib,dbs/rdflib