cubicweb #4745929 RDF view crash with non final relation equivalence [validation pending]

For instance, I have:

xy.add_equivalence('Dataset dataset_publisher', 'dct:publisher')

where:

class dataset_distribution(RelationDefinition):
    subject = 'Dataset'
    object  = 'Distribution'
    cardinality = '?*'
    description = _('relate a Dataset to an available Distribution')

And calling the RDF view on a Dataset entity leads to:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/application.py", line 461, in core_handle
    result = controller.publish(rset=rset)
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/basecontrollers.py", line 136, in publish
    rset=rset, view=view)
  File "/usr/lib/python2.7/dist-packages/cubicweb/cwvreg.py", line 388, in main_template
    res = obj.render(**kwargs)
  File "/usr/lib/python2.7/dist-packages/cubicweb/view.py", line 137, in render
    view_func(**context)
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/basetemplates.py", line 120, in call
    view.render()
  File "/usr/lib/python2.7/dist-packages/cubicweb/view.py", line 137, in render
    view_func(**context)
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/rdf.py", line 59, in call
    self.entity2graph(graph, entity)
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/rdf.py", line 97, in entity2graph
    add( (cwuri, urijoin(item), URIRef(related.cwuri)) )
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/rdf.py", line 40, in urijoin
    base, ext = item
ValueError: too many values to unpack
prioritynormal
typebug
done in3.19.11
load1.000
load left0.000
closed by#a12e4459eee5 [web/views/rdf] Take the second element of XY equivalent for non final relation
patch[web/views/rdf] Take the second element of XY equivalent for non final relation [applied]