title: Get raw HTTP response with Retrofit
body: <p>I want to get the raw http response from my API REST. I have tried with this interface:</p>
  
  <pre><code>@POST("/login")
  @FormUrlEncoded
  Call&lt;retrofit.Response&gt; login(@Field("username") String login, @Field("password") String pass,
                       @Field("appName") String appName, @Field("appKey") String appKey);
  </code></pre>
  
  <p>But I get:</p>
  
  <blockquote>
    <p>java.lang.IllegalArgumentException: Unable to create call adapter for
    retrofit.Call
        for method Api.login</p>
  </blockquote>
  
  <p>I create <code>Retrofit</code> this way:</p>
  
  <pre><code>Retrofit.Builder retrofitBuilder = new Retrofit.Builder();
  retrofitBuilder.addConverterFactory(JacksonConverterFactory.create());
  Retrofit retrofitAdapter = retrofitBuilder.baseUrl(baseUrl).build();
  return retrofitAdapter.create(apiClass);
  </code></pre>