title: Spring ResponseStatusException does not return reason
body: <p>I have a very simple <code>@RestController</code>, and I'm trying to set a custom error message. But for some reason, the <code>message</code> for the error is not showing up.</p>
  <p>This is my controller:</p>
  <pre><code>@RestController
  @RequestMapping(&quot;openPharmacy&quot;)
  public class OpenPharmacyController {
  
  
      @PostMapping
      public String findNumberOfSurgeries(@RequestBody String skuLockRequest) {
          throw new ResponseStatusException(HttpStatus.BAD_REQUEST, &quot;This postcode is not valid&quot;);
      }
  
  }
  </code></pre>
  <p>This is the response that I get:</p>
  <pre><code>{
      &quot;timestamp&quot;: &quot;2020-06-24T17:44:20.194+00:00&quot;,
      &quot;status&quot;: 400,
      &quot;error&quot;: &quot;Bad Request&quot;,
      &quot;message&quot;: &quot;&quot;,
      &quot;path&quot;: &quot;/openPharmacy/&quot;
  }
  </code></pre>
  <p>I'm passing a JSON, but I'm not validating anything, I'm just trying to set the custom message. If I change the status code, I see that on the response, but the <code>message</code> is always empty.</p>
  <p>Why is this not working like expected? This is such a simple example that I can't see what may be missing. When I debug the code I can see that the error message has all the fields set. But for some reason, the message is never set on the response.</p>