Fix docker build

[luiarthur]

Currently failing because ursa version is not available anymore. (Might be ursa --version.)

[mikegros]

I think I already fixed this but didnt think it needed tagging. Should i have tagged to 0.14.1?

[luiarthur]

Yes, that should be fine. Yes, I'll tag to trigger a container build.

[luiarthur]

Fixed by #154.