code: public static void addDeprecation(String key, String newKey) {
  		addDeprecation(key, new String[] {newKey}, null);
  	}
docs: Adds the deprecated key to the global deprecation map when no custom
  message is provided.
  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 Key that is to be deprecated
  @param newKey key that takes up the value of deprecated key