[telepathy-gabble/master] _elem_add(): clarify error message

[Dafydd Harries]

---
 tests/twisted/gabbletest.py |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/tests/twisted/gabbletest.py b/tests/twisted/gabbletest.py
index 094e58e..dc9ecea 100644
--- a/tests/twisted/gabbletest.py
+++ b/tests/twisted/gabbletest.py
@@ -464,7 +464,8 @@ def _elem_add(elem, *children):
         elif isinstance(child, unicode):
             elem.addContent(child)
         else:
-            raise ValueError('invalid child object %r', child)
+            raise ValueError(
+                'invalid child object %r (must be element or unicode)', child)
 
 def elem(a, b=None, **kw):
     r"""
-- 
1.5.6.5