get_relationship() is failing with KeyError: 'relationship'.
Seems to be that py2neo is trying to get the URL from self.metadata['relationship'], but this key doesn't exist.
self.metadata is populated from Neo4j service root, but the service root does not return "relationship" (only relationship_index and relationship_types) --> http://docs.neo4j.org/chunked/milestone/rest-api-service-root.html
So I'm not sure how get_relationship() can work as is?
I've modified get_relationship from:
return Relationship(self.metadata['relationship'] + "/" + str(id), graph_db=self)
return Relationship(str(self._uri) + "relationship/" + str(id), graph_db=self)
... and it's working for me now.
I have the same issue.