Return a call stack for better error handling

Author: wattdave

clouddriver-aws/src/main/groovy/com/netflix/spinnaker/clouddriver/aws/provider/agent/ClusterCachingAgent.groovy

@@ -550,7 +550,9 @@ class ClusterCachingAgent implements CachingAgent, OnDemandAgent, AccountAware,
           cacheTargetGroups(data, targetGroups)
           cacheLaunchTemplate(data, launchTemplates)
         } catch (Exception ex) {
-          log.warn("Failed to cache ${asg.autoScalingGroupName} in ${account.name}/${region}", ex)
+          StringWriter sw = new StringWriter()
+          ex.printStackTrace(sw)
+          log.warn("Failed to cache ${asg.autoScalingGroupName} in ${account.name}/${region}: ${sw.toString()}", ex)
         }
       }
     }