More useful error messages

[ershockley]

This issue will probably never be fully resolved, but it'd be nice to print useful information if a request returns non-200. For example, when updating the database there are required fields and expected types. If there is a field missing or a wrong type it'd be nice to state which fields are the problem, or at least print out what the requirements are.

[yuema137]

I think it's good enough now especially with #86