Make exceptions picklable on Python 2.X

Author: immerrr

jsonschema/exceptions.py

@@ -41,6 +41,11 @@ def __init__(
  for error in context:
  error.parent = self
 
+ # Initialize exception args or otherwise __reduce__ will return empty
+ # args tuple on Py2.7 and unpickling will fail because init requires at
+ # least one argument.
+ self.args = (message,)
+
  def __repr__(self):
  return "<%s: %r>" % (self.__class__.__name__, self.message)
 

jsonschema/tests/test_exceptions.py

@@ -1,3 +1,4 @@
+import pickle
 import textwrap
 
 from jsonschema import Draft4Validator, exceptions
@@ -380,3 +381,20 @@ def test_str_works_with_instances_having_overriden_eq_operator(self):
  )
  str(error)
  self.assertFalse(instance.__eq__.called)
+
+
+class TestErrorsArePicklable(unittest.TestCase):
+ def test_validation_error_is_picklable(self):
+ err = exceptions.ValidationError(
+ "a message",
+ validator="foo",
+ instance="bar",
+ validator_value="some",
+ schema="schema",
+ )
+ unpickled = pickle.loads(pickle.dumps(err))
+ self.assertEqual(unpickled.message, "a message")
+ self.assertEqual(unpickled.validator, "foo")
+ self.assertEqual(unpickled.instance, "bar")
+ self.assertEqual(unpickled.validator_value, "some")
+ self.assertEqual(unpickled.schema, "schema")