[python3] use python3 dmlc tracker in rabit tests (#525)

scripts/lint.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # pylint: disable=protected-access, unused-variable, locally-disabled, len-as-condition
 """Lint helper to generate lint summary of source.
 

tracker/dmlc-submit

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 import sys
 import os
 curr_path = os.path.dirname(os.path.abspath(os.path.expanduser(__file__)))

tracker/dmlc_tracker/kubernetes.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """
 DMLC submission script by kubernetes
 

tracker/dmlc_tracker/launcher.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # pylint: disable=invalid-name
 """The container launcher script that launches DMLC with the right env variable."""
 import glob

tracker/dmlc_tracker/mesos.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """
 DMLC submission script by mesos
 

tracker/dmlc_tracker/ssh.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """
 DMLC submission script by ssh