Deal with 404 response when checking for artifacts

ci/images/releasescripts/src/main/java/io/spring/concourse/releasescripts/bintray/BintrayService.java

@@ -101,8 +101,13 @@ public class BintrayService {
 		try {
 			waitAtMost(timeout).with().pollDelay(Duration.ZERO).pollInterval(pollInterval).until(() -> {
 				logger.debug("Checking bintray");
+				try {
 					PackageFile[] published = this.restTemplate.exchange(request, PackageFile[].class).getBody();
 					return hasPublishedAll(published, requiredDigests);
+				}
+				catch (HttpClientErrorException.NotFound ex) {
+					return false;
+				}
 			});
 		}
 		catch (ConditionTimeoutException ex) {