When the CLI hits a server error, it prints out a lot of HTML

[bowlofeggs]

The Bodhi CLI prints out a lot of HTML when it hits server errors, such as what happened in #3024. The server should not return HTML upon requests from the CLI, but instead should return a standardized error struct (which needs to be defined as part of solving this issue). Then the CLI should look for this error struct and format the error in a human readable fashion.

[sebwoj]

@bowlofeggs Since we have #3042, can we close it?

[bowlofeggs]

Yep, thanks!