MAINT: Explicitly convert map to list when converting answer key values.

For compatibility with iterator version of map in Python 3.

Also always use iterator version of map,
so that code path is exercised in Python 2.

tests/risk/answer_key.py

@@ -22,6 +22,8 @@ import pytz
 import xlrd
 import requests
 
+from six.moves import map
+
 
 def col_letter_to_index(col_letter):
     # Only supports single letter,
@@ -288,7 +290,8 @@ class AnswerKey(object):
 
     def get_values(self, data_index):
         value_parser = self.value_type_to_value_func[data_index.value_type]
-        return map(value_parser, self.get_raw_values(data_index))
+        return [value for value in
+                map(value_parser, self.get_raw_values(data_index))]
 
 
 ANSWER_KEY = AnswerKey()