code: protected boolean isIncludeStackTrace(HttpServletRequest request,
  			MediaType produces) {
  		IncludeStacktrace include = getErrorProperties().getIncludeStacktrace();
  		if (include == IncludeStacktrace.ALWAYS) {
  			return true;
  		}
  		if (include == IncludeStacktrace.ON_TRACE_PARAM) {
  			return getTraceParameter(request);
  		}
  		return false;
  	}
docs: Determine if the stacktrace attribute should be included.
  @param request the source request
  @param produces the media type produced (or {@code MediaType.ALL})
  @return if the stacktrace attribute should be included