--- a/server/serverctl.py	Thu May 28 11:35:56 2009 +0200
+++ b/server/serverctl.py	Thu May 28 11:37:27 2009 +0200
@@ -119,7 +119,7 @@
                     _sconfig.set_option(attr, val)
             sconfig = _sconfig
         optsbysect = list(sconfig.options_by_section())
-        assert len(optsbysect) == 1
+        assert len(optsbysect) == 1, 'all options for a source should be in the same group'
         ini_format_section(stream, uri, optsbysect[0][1])
         if hasattr(sconfig, 'adapter'):
             print >> stream