Merge pull request #136 from jimkring/patch-1

add required arg `backtrack_causes` to `get_preferences()` override

examples/reporter_demo.py

@@ -73,7 +73,14 @@ def __init__(self, index):
     def identify(self, requirement_or_candidate):
         return requirement_or_candidate.name
 
-    def get_preference(self, identifier, resolutions, candidates, information):
+    def get_preference(
+        self,
+        identifier,
+        resolutions,
+        candidates,
+        information,
+        backtrack_causes,
+    ):
         return sum(1 for _ in candidates[identifier])
 
     def find_matches(self, identifier, requirements, incompatibilities):