Added more expressive description of an error.

1 files changed, 5 insertions, 1 deletions

diff --git a/markdown/odict.py b/markdown/odict.py
index d545a46..4de4424 100644
--- a/markdown/odict.py
+++ b/markdown/odict.py
@@ -117,7 +117,11 @@ class OrderedDict(dict):
 
     def index(self, key):
         """ Return the index of a given key. """
-        return self.keyOrder.index(key)
+        try:
+            return self.keyOrder.index(key)
+        except ValueError, e:
+            raise KeyError("Element '%s' was not found in OrderedDict" % key)
+            
 
     def index_for_location(self, location):
         """ Return index or None for a given location. """