Fixed exception printing

Author: syrusakbary

graphql/execution/base.py

@@ -4,24 +4,14 @@
 from ..error import GraphQLError
 from ..language import ast
 from ..pyutils.default_ordered_dict import DefaultOrderedDict
-from ..type.definition import GraphQLInterfaceType, GraphQLUnionType
+from ..type.definition import Undefined, GraphQLInterfaceType, GraphQLUnionType
 from ..type.directives import GraphQLIncludeDirective, GraphQLSkipDirective
 from ..type.introspection import (SchemaMetaFieldDef, TypeMetaFieldDef,
                                   TypeNameMetaFieldDef)
 from ..utils.type_from_ast import type_from_ast
 from .values import get_argument_values, get_variable_values
 
 
-class _Undefined(object):
-    def __bool__(self):
-        return False
-
-    __nonzero__ = __bool__
-
-
-Undefined = _Undefined()
-
-
 class ExecutionContext(object):
     """Data that must be available at all points during query execution.
 
@@ -93,7 +83,7 @@ def get_argument_values(self, field_def, field_ast):
         return result
 
     def report_error(self, error, traceback=None):
-        sys.excepthook(type(error), str(error), getattr(error, 'stack', None) or traceback)
+        sys.excepthook(type(error), error, getattr(error, 'stack', None) or traceback)
         self.errors.append(error)
 
     def get_sub_fields(self, return_type, field_asts):

graphql/type/__init__.py

@@ -19,7 +19,8 @@
     is_leaf_type,
     is_type,
     get_nullable_type,
-    is_output_type
+    is_output_type,
+    Undefined
 )
 from .directives import (
     # "Enum" of Directive locations

graphql/type/definition.py

@@ -7,6 +7,16 @@
 from ..utils.assert_valid_name import assert_valid_name
 
 
+class _Undefined(object):
+    def __bool__(self):
+        return False
+
+    __nonzero__ = __bool__
+
+
+Undefined = _Undefined()
+
+
 def is_type(type):
     return isinstance(type, (
         GraphQLScalarType,