Problem in Creating user

Hi, I am trying to set up Tyk in Ubuntu. While I am trying to create users, it shows traceback in python.I am using python 2.7.6. I have also attached the screenshot of the terminal. Please do check.Python_error

Do you have any other python versions installed? Which version of ubuntu are you running?

I am using ubuntu 15.10. I have only Python 2.7.6 installed