Zero value exceptions now return float('NaN')

Author: maciekrb

mapreduceutils/modifiers/primitives.py

@@ -470,4 +470,5 @@ def _evaluate(self):
       raise ValueError(msg.format(expression, operands))
     except ZeroDivisionError:
       msg = "Zero division for expression {} with operands {}"
-      raise ValueError(msg.format(expression, operands))
+      logging.warn(msg.format(expression, operands))
+      return float('NaN')