[Culprit-Finder] Add generator cache decorator.

appengine/findit/crash/loglinear/changelist_features/min_distance.py

Index: appengine/findit/crash/loglinear/changelist_features/min_distance.py
diff --git a/appengine/findit/crash/loglinear/changelist_features/min_distance.py b/appengine/findit/crash/loglinear/changelist_features/min_distance.py
index 480cf8961c120ad78813103382e8e11d0b78999f..4f985a45bd07391855796ab19df89d9ea37f69ad 100644
--- a/appengine/findit/crash/loglinear/changelist_features/min_distance.py
+++ b/appengine/findit/crash/loglinear/changelist_features/min_distance.py
@@ -73,7 +73,9 @@ class MinDistanceFeature(Feature):
       return FeatureValue(
           name = self.name,
           value = LogLinearlyScaled(float(min_distance), float(self._maximum)),
-          reason = ('Minimum distance is %d' % min_distance),
+          reason = ('Minimum distance is %d' % min_distance
+                    if not math.isinf(min_distance) else
+                    'Minimum distance is infinity'),
           changed_files = self._ChangedFiles(suspect),
       )