@Override
	public void describeMismatch(Object item, Description description) {
		AbstractMetricSink sink = (AbstractMetricSink) item;
		description.appendText(sink.getDslName()).appendText(" named '").appendText(sink.getName()).appendText(
				"' did not exist");
	}
A matcher that will assert that the {@code <metric type> list} shell command returns a list that contains the
expected metric.

@param <T> the type of metric sink fixture this is matching
@author Eric Bottard
@author Marius Bogoevici
spring-xd-shell/src/test/java/org/springframework/xd/shell/command/fixtures/MetricExistsMatcher.java