edge.replace() fails for edge with cardinality=ONE

[na-ka-na]

Example code:

class Site(StructuredNode):
   pass

class Node(StructuredNode):
   site = RelationshipTo('Site', 'site', cardinality=One)

site = Site()
node = Node()
node.site.connect(site)

site2 = Site()
node.site.connect(site2) # fails
node.site.replace(site2) # fails

# The only pattern that I could find that works is
existing_site = node.site.get_or_none()
if existing_site:
    node.site.reconnect(existing_site, site)
else:
    node.site.connect(site)

Suggestion: make replace() work so that we don't have to query the existing_site

[mariusconjeaud]

Checked this and I get an error too on replace for Cardinality=One. Marking as bug.