I recently faced an issue with Ryu SDN controller framework. The error was:
ImportError: No module named oslo.config.cfg
And solved by doing (in the root directory of Ryu to upgrade the controller):
# pip2 install --upgrade ryu
I’m not sure, but I guess it was a deprecated version of OSLO package that was installed on my system or, maybe, the version of OSLO package that I had was superior than Ryu 3.21 needed (API’s parameters or names might have changed).