App IDs ending in /tasks, etc. should be considered invalid

{
  "id": "/le-group/tasks",
  "args": ["sh", "-c", "sleep 3601"],
  "container": {
    "type": "DOCKER",
    "docker": {
      "forcePullImage": false,
      "image": "alpine",
      "privileged": false
    }
  },
  "cpus": 0.1,
  "instances": 0,
  "mem": 64
}

$ cat p4wn3d.json | http POST :2016/v2/apps

HTTP/1.1 201 Created
Cache-Control: no-cache, no-store, must-revalidate
Content-Type: application/json; qs=2
Date: Sat, 06 May 2017 06:57:08 GMT
Expires: 0
Location: http://localhost:2016/v2/apps/le-group/tasks
Marathon-Deployment-Id: c55af223-fd87-42c8-89a4-f3a9f8729609
Pragma: no-cache
Transfer-Encoding: chunked
X-Marathon-Leader: http://Tim-Harper.local:2016

{
    "args": [
        "sh",
        "-c",
        "sleep 3601"
    ],
    "backoffFactor": 1.15,
    "backoffSeconds": 1,
    "container": {
        "docker": {
            "forcePullImage": false,
            "image": "alpine",
            "parameters": [],
            "privileged": false
        },
        "type": "DOCKER",
        "volumes": []
    },
    "cpus": 0.1,
    "deployments": [
        {
            "id": "c55af223-fd87-42c8-89a4-f3a9f8729609"
        }
    ],
    "disk": 0,
    "executor": "",
    "gpus": 0,
    "id": "/le-group/tasks",
    "instances": 0,
    "killSelection": "YOUNGEST_FIRST",
    "labels": {},
    "maxLaunchDelaySeconds": 3600,
    "mem": 64,
    "networks": [
        {
            "mode": "host"
        }
    ],
    "portDefinitions": [
        {
            "name": "default",
            "port": 0,
            "protocol": "tcp"
        }
    ],
    "requirePorts": false,
    "tasks": [],
    "tasksHealthy": 0,
    "tasksRunning": 0,
    "tasksStaged": 0,
    "tasksUnhealthy": 0,
    "unreachableStrategy": {
        "expungeAfterSeconds": 600,
        "inactiveAfterSeconds": 300
    },
    "upgradeStrategy": {
        "maximumOverCapacity": 1,
        "minimumHealthCapacity": 1
    },
    "version": "2017-05-06T06:57:08.051Z"
}

$ http :2016/v2/apps/le-group/tasks | jq .
{
  "message": "App '/le-group' does not exist"
}

00:59 $ http DELETE :2016/v2/apps/le-group/tasks
{
    "message": "App '/le-group' does not exist"
}