code: private String getErrorForUnknownService(String id) {
  		StringBuffer error = new StringBuffer();
  		error.append("Services path: " + ServiceConfigurationManager.CONFIGURATION_DIR);
  		error.append("The service with id: " + id + " is not registered");
  
  		error.append("\n Available services are: ");
  
  		Set<String> keys = serviceManager.getRegisteredConfigurations().keySet();
  
  		Iterator<String> it = keys.iterator();
  
  		while (it.hasNext()) {
  			error.append(it.next()).append(" ");
  		}
  
  		return error.toString();
  	}
docs: Exception text when a service requested is not registered into the
  library
  
  @param id
  The id of the service not found
  @return The Exception text to show to the user