message: reactor.http.StatusCode: Pretty print 422 Unprocessable Entity.
diff: @@ -119,6 +119,9 @@ namespace elle
  case StatusCode::Expectation_Failed:
  output << "Expectation Failed";
  break;
  + case StatusCode::Unprocessable_Entity:
  + output << "Unprocessable Entity";
  + break;
  case StatusCode::Too_Many_Requests:
  output << "Too Many Requests";
  break;
  