From bb7976a75f2a86313b718f62db6ed624d00bf02d Mon Sep 17 00:00:00 2001
From: Syrus Akbary <me@syrusakbary.com>
Date: Mon, 14 Nov 2016 20:27:06 -0800
Subject: [PATCH] Improved ConnectionField exception message. Fixed #356

---
 graphene/relay/connection.py      |  2 +-
 graphene/relay/node.py            |  6 +++---
 graphene/tests/issues/test_356.py | 24 ++++++++++++++++++++++++
 3 files changed, 28 insertions(+), 4 deletions(-)
 create mode 100644 graphene/tests/issues/test_356.py

diff --git a/graphene/relay/connection.py b/graphene/relay/connection.py
index 72f018dc..339e4266 100644
--- a/graphene/relay/connection.py
+++ b/graphene/relay/connection.py
@@ -115,7 +115,7 @@ class IterableConnectionField(Field):
             connection_type = type
         assert issubclass(connection_type, Connection), (
             '{} type have to be a subclass of Connection. Received "{}".'
-        ).format(str(self), connection_type)
+        ).format(self.__class__.__name__, connection_type)
         return connection_type
 
     @classmethod
diff --git a/graphene/relay/node.py b/graphene/relay/node.py
index 9d795875..3db30e93 100644
--- a/graphene/relay/node.py
+++ b/graphene/relay/node.py
@@ -12,9 +12,9 @@ def is_node(objecttype):
     '''
     Check if the given objecttype has Node as an interface
     '''
-    assert issubclass(objecttype, ObjectType), (
-        'Only ObjectTypes can have a Node interface. Received %s'
-    ) % objecttype
+    if not issubclass(objecttype, ObjectType):
+        return False
+
     for i in objecttype._meta.interfaces:
         if issubclass(i, Node):
             return True
diff --git a/graphene/tests/issues/test_356.py b/graphene/tests/issues/test_356.py
new file mode 100644
index 00000000..605594e1
--- /dev/null
+++ b/graphene/tests/issues/test_356.py
@@ -0,0 +1,24 @@
+# https://github.com/graphql-python/graphene/issues/356
+
+import pytest
+import graphene
+from graphene import relay
+
+class SomeTypeOne(graphene.ObjectType):
+    pass
+
+class SomeTypeTwo(graphene.ObjectType):
+    pass
+
+class MyUnion(graphene.Union):
+    class Meta:
+        types = (SomeTypeOne, SomeTypeTwo)
+
+def test_issue():
+    with pytest.raises(Exception) as exc_info:
+        class Query(graphene.ObjectType):
+            things = relay.ConnectionField(MyUnion)
+
+        schema = graphene.Schema(query=Query)
+
+    assert str(exc_info.value) == 'IterableConnectionField type have to be a subclass of Connection. Received "MyUnion".'