Add error response field to InvalidResponseCodeException

[chrisfillmore]

[REQUIRED] Use case description

I would like to include the HTTP response body in an InvalidResponseCodeException, so that I can read the response.

In particular, our license server sends back specific error codes which we need to triage.

Proposed solution

Add a new field to InvalidResponseCodeException which stores the value returned from HttpURLConnection#getErrorStream() (or string equivalent).

Alternatives considered

We could make our license request without using Exo's APIs. But I think making the change in Exo would be useful for everyone, and backwards-compatible.

I can make a pull request, with your support.

[ojw28]

#3920 was requesting this as well.

@chrisfillmore - Is there a reason to use 403 rather than 200 for this case (see the issue ref'd above for more information)?
@jrocharodrigues - Did you implement this already, or did you do it differently?

[chrisfillmore]

In our particular case we get HTTP 400 with an error code in the response body.

It's not feasible for us to change the HTTP status from the license proxy; this would have a far-reaching impact on other client platforms we support. But I also don't think that 200 is an appropriate status for this response. The server wants to indicate the request is bad, hence 400.

Is there a particular reason you'd prefer not to add this field? I'll admit, to me this seems a straightforward change with obvious benefit, without breaking anything. Am I missing something?