kubernetes tracker meeting Empty domain

Hi ! I'm trying to use dmlc-submit to submit a kubernetes job , and i meet the bug following:

```
To check each log, try 'kubectl logs job/{{role}}-{{jobname}}-{{workerID}}'
Traceback (most recent call last):
File "./dmlc-submit", line 9, in
submit.main()
File "/home/tusimple/incubator-mxnet/3rdparty/dmlc-core/tracker/dmlc_tracker/submit.py", line 54, in main
kubernetes.submit(args)
File "/home/tusimple/incubator-mxnet/3rdparty/dmlc-core/tracker/dmlc_tracker/kubernetes.py", line 143, in submit
pscmd="echo \"To check each log, try 'kubectl logs job/{{role}}-{{jobname}}-{{workerID}}'\"")
File "/home/tusimple/incubator-mxnet/3rdparty/dmlc-core/tracker/dmlc_tracker/tracker.py", line 428, in submit
fun_submit(nworker, nserver, envs)
File "/home/tusimple/incubator-mxnet/3rdparty/dmlc-core/tracker/dmlc_tracker/kubernetes.py", line 129, in kubernetes_submit
resp = k8s_batch.create_namespaced_job(namespace=args.kube_namespace, body=mn_sh_job)
File "build/bdist.linux-x86_64/egg/kubernetes/client/apis/batch_v1_api.py", line 58, in create_namespaced_job
File "build/bdist.linux-x86_64/egg/kubernetes/client/apis/batch_v1_api.py", line 143, in create_namespaced_job_with_http_info
File "build/bdist.linux-x86_64/egg/kubernetes/client/api_client.py", line 321, in call_api
File "build/bdist.linux-x86_64/egg/kubernetes/client/api_client.py", line 155, in __call_api
File "build/bdist.linux-x86_64/egg/kubernetes/client/api_client.py", line 364, in request
File "build/bdist.linux-x86_64/egg/kubernetes/client/rest.py", line 266, in POST
File "build/bdist.linux-x86_64/egg/kubernetes/client/rest.py", line 166, in request
File "/usr/local/lib/python2.7/dist-packages/urllib3/request.py", line 72, in request
**urlopen_kw)
File "/usr/local/lib/python2.7/dist-packages/urllib3/request.py", line 150, in request_encode_body
return self.urlopen(method, url, **extra_kw)
File "/usr/local/lib/python2.7/dist-packages/urllib3/poolmanager.py", line 322, in urlopen
response = conn.urlopen(method, u.request_uri, **kw)
File "/usr/local/lib/python2.7/dist-packages/urllib3/connectionpool.py", line 600, in urlopen
chunked=chunked)
File "/usr/local/lib/python2.7/dist-packages/urllib3/connectionpool.py", line 343, in _make_request
self._validate_conn(conn)
File "/usr/local/lib/python2.7/dist-packages/urllib3/connectionpool.py", line 849, in _validate_conn
conn.connect()
File "/usr/local/lib/python2.7/dist-packages/urllib3/connection.py", line 367, in connect
cert = self.sock.getpeercert()
File "/usr/local/lib/python2.7/dist-packages/urllib3/contrib/pyopenssl.py", line 351, in getpeercert
'subjectAltName': get_subj_alt_name(x509)
File "/usr/local/lib/python2.7/dist-packages/urllib3/contrib/pyopenssl.py", line 228, in get_subj_alt_name
for name in ext.get_values_for_type(x509.DNSName)
File "/usr/local/lib/python2.7/dist-packages/urllib3/contrib/pyopenssl.py", line 181, in _dnsname_to_stdlib
name = idna_encode(name)
File "/usr/local/lib/python2.7/dist-packages/urllib3/contrib/pyopenssl.py", line 179, in idna_encode
return idna.encode(name)
File "/usr/local/lib/python2.7/dist-packages/idna/core.py", line 350, in encode
raise IDNAError('Empty domain')
idna.core.IDNAError: Empty domain
```

i'm using the command below:

```
./dmlc-submit --cluster kubernetes --jobname test --num-workers
3 --num-server 1 --kube-worker-image jzp1025/mxnet:test --kube-server-image jzp1025/mxnet:test python /incubator-mxnet/example/image-classification/train_mnist.py --network=resnet --num-layers=110 --batch-size=128 --kv-store=dist_device_sync
```
looking for some help , thanks !