当使用Retrofit 2.0 Observables时出现错误，如何获取Response body

I am using Retrofit 2.0 to make api calls that return Observables. It all works good when the call went through fine and the response is as expected. Now let's say we have an error response, it throws an onError. I would like to read the response body even when it is an Error.I am using Retrofit 2.0 to make api calls that