code: public static void addDeprecation(String key, String newKey,
  	                                  String customMessage) {
  		addDeprecation(key, new String[] {newKey}, customMessage);
  	}
docs: Adds the deprecated key to the global deprecation map.
  It does not override any existing entries in the deprecation map.
  This is to be used only by the developers in order to add deprecation of
  keys, and attempts to call this method after loading resources once,
  would lead to <tt>UnsupportedOperationException</tt>
  
  If you have multiple deprecation entries to add, it is more efficient to
  use #addDeprecations(DeprecationDelta[] deltas) instead.
  
  @param key
  @param newKey
  @param customMessage