Made DateTime types return GraphQLError on fail

This change makes it so that when an incorrectly formatted date string gets passed to a Date / Time argument a GraphQLError is returned rather than a GraphQLLocatedError. Since Date / Time are types, their errors should not be in the same class as errors in your application. This is also inline with how other types work in graphene (graphene.Int, graphene.Float)

Author: anisjonischkeit

graphene/types/datetime.py

@@ -38,8 +38,10 @@ def parse_literal(cls, node):
 
     @staticmethod
     def parse_value(value):
-        return iso8601.parse_date(value).date()
-
+        try:
+            return iso8601.parse_date(value).date()
+        except iso8601.ParseError:
+            return None
 
 class DateTime(Scalar):
     '''
@@ -62,8 +64,10 @@ def parse_literal(cls, node):
 
     @staticmethod
     def parse_value(value):
-        return iso8601.parse_date(value)
-
+        try:
+            return iso8601.parse_date(value)
+        except iso8601.ParseError:
+            return None
 
 class Time(Scalar):
     '''
@@ -87,5 +91,8 @@ def parse_literal(cls, node):
 
     @classmethod
     def parse_value(cls, value):
-        dt = iso8601.parse_date('{}T{}'.format(cls.epoch_date, value))
-        return datetime.time(dt.hour, dt.minute, dt.second, dt.microsecond, dt.tzinfo)
+        try:
+            dt = iso8601.parse_date('{}T{}'.format(cls.epoch_date, value))
+            return datetime.time(dt.hour, dt.minute, dt.second, dt.microsecond, dt.tzinfo)
+        except iso8601.ParseError:
+            return None