config-prettyfaces/src/main/java/com/ocpsoft/pretty/PrettyContext.java
public void sendError(int code, String message)
   {
      FacesContext facesContext = FacesContext.getCurrentInstance();
      Assert.notNull(facesContext, "FacesContext argument was null.");

      Object response = facesContext.getExternalContext().getResponse();
      if (response instanceof HttpServletResponse)
      {
         sendError(code, message, (HttpServletResponse) response);
         facesContext.responseComplete();
      }

   }
public void sendError(int code, String message)
   {
      FacesContext facesContext = FacesContext.getCurrentInstance();
      Assert.notNull(facesContext, "FacesContext argument was null.");

      Object response = facesContext.getExternalContext().getResponse();
      if (response instanceof HttpServletResponse)
      {
         sendError(code, message, (HttpServletResponse) response);
         facesContext.responseComplete();
      }

   }
<p>
Sends an error response to the client using the specified HTTP status
code.
</p>
<p>
Please note that this method can only be called from within the JSF
lifecycle as it needs the {@link FacesContext} to obtain the
{@link HttpServletResponse}. Please use
{@link #sendError(int, String, HttpServletResponse)} in all other
cases.
</p>

@param code the error status code
@param message the descriptive message
@see HttpServletResponse#sendError(int, String)