code: @Cmd
  	public void optional(final Closure<Void> closure) {
  		log.info("Executing optional block ...");
  		try {
  			closure.call();
  		} catch (final Exception ex) {
  			log.error("Exception executing optional block: " + ex.getMessage(), ex);
  			errors.add(ex);
  		} catch (AssertionError err) {
  			log.error("Assertion failed executing optional block: " + err.getMessage(), err);
  			errors.add(err);
  		}
  		log.info("... finished execution of optional block");
  	}
docs: Runs the specified closure catching any exception that might occur during execution.
  
  @param closure
  the {@link Closure} representing a Groovy block