#50 Overlaying geometries KOM + OEK

* removes unused messages
* adds geometry conflict message rendering for KOM and OEK
* removes unused methods in GeoReferencedMixin
* generalizes geometrical lookup for conflicts from overlaps to intersects

konova/forms.py

@@ -282,11 +282,13 @@ class SimpleGeomForm(BaseForm):
 
         """
         try:
+            if self.instance is None or self.instance.geometry is None:
+                raise LookupError
             geometry = self.instance.geometry
             geometry.geom = self.cleaned_data.get("geom", MultiPolygon(srid=DEFAULT_SRID))
             geometry.modified = action
             geometry.save()
-        except AttributeError:
+        except LookupError:
             # No geometry or linked instance holding a geometry exist --> create a new one!
             geometry = Geometry.objects.create(
                 geom=self.cleaned_data.get("geom", MultiPolygon(srid=DEFAULT_SRID)),