Fix issue2551129 - Template not found return 500 and traceback Handle traceback caused when requested @template is not found. Moved scope of try to include call to self.selectTemplate. Patch provided by Cedric Krier. Additional patch to make this case return 400 error since it is a client caused error. Test case added.

try:
    # Python 3+.
    from xmlrpc import client, server
    server.SimpleXMLRPCDispatcher
except (ImportError, AttributeError):
    # Python 2.
    import xmlrpclib as client  # noqa: F401
    import SimpleXMLRPCServer as server