code: private JSONNavi<?> failure(String err, Object jPathPostfix) {
  		failure = true;
  		StringBuilder sb = new StringBuilder();
  		sb.append("Error: ");
  		sb.append(err);
  		sb.append(" at ");
  		sb.append(getJPath());
  		if (jPathPostfix != null)
  			if (jPathPostfix instanceof Integer)
  				sb.append('[').append(jPathPostfix).append(']');
  			else
  				sb.append('/').append(jPathPostfix);
  		this.failureMessage = sb.toString();
  		return this;
  	}
docs: Internally log errors.