code: private void unwrapIO(RedmineException orig, String tag) throws IOException {
  		Throwable e = orig;
  		while (e != null) {
  			if (e instanceof MarkedIOException) {
  				final MarkedIOException marked = (MarkedIOException) e;
  				if (tag.equals(marked.getTag()))
  					throw marked.getIOException();
  			}
  			e = e.getCause();
  		}
  	}
docs: Unwraps an IO.
  
  @param e
  exception to unwrap.
  @param tag
  target tag.
  @throws IOException
  @throws RedmineException