Add the broken scope to the ValueError exception for easier debugging, add test for failure case.

2 files changed, 3 insertions, 1 deletions

diff --git a/oauthlib/oauth2/rfc6749/utils.py b/oauthlib/oauth2/rfc6749/utils.py
index 49c3a2f..870ac32 100644
--- a/oauthlib/oauth2/rfc6749/utils.py
+++ b/oauthlib/oauth2/rfc6749/utils.py
@@ -27,7 +27,7 @@ def list_to_scope(scope):
     elif isinstance(scope, (set, tuple, list)):
         return " ".join([unicode_type(s) for s in scope])
     else:
-        raise ValueError("Invalid scope, must be string or list.")
+        raise ValueError("Invalid scope (%s), must be string, tuple, set, or list." % scope)
 
 
 def scope_to_list(scope):
diff --git a/tests/oauth2/rfc6749/test_utils.py b/tests/oauth2/rfc6749/test_utils.py
index 573b187..691de76 100644
--- a/tests/oauth2/rfc6749/test_utils.py
+++ b/tests/oauth2/rfc6749/test_utils.py
@@ -85,6 +85,8 @@ class UtilsTests(TestCase):
         for x in string_list:
             assert x in set_scope
 
+        self.assertRaises(ValueError, list_to_scope, object()) 
+
     def test_scope_to_list(self):
         expected = ['foo', 'bar', 'baz']