Add link to bug

So we know if we can remove this in the future, or at least have context
around why it's there.

Change-Id: I4e4bdcd6a01e8c1071045bbe1310cbdf4195ec27
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

oslo_db/sqlalchemy/exc_filters.py

@@ -431,6 +431,7 @@ def handler(context):
             yield _registry['*']
 
     # do not reraise for our own exceptions
+    # https://github.com/sqlalchemy/sqlalchemy/issues/10116
     if isinstance(context.original_exception, exception.DBError):
         return