Adding cohort co-owner does not work (endpoint error?)

[jlumbroso]

When trying to use the UI to add a co-owner to a cohort, the Javascript Console records the following events (each error is due to a new click on the button).

[jlumbroso]

I'll go on a hunch, and say that this could be due to the fact that "marshini@princeton.edu" is not an existing user of the system. The next step would be to try to add as co-owner an existing user of the system.