use python3 in hack

hack/boilerplate/boilerplate.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2015 The Kubernetes Authors.
 #
@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import print_function
-
 import argparse
 import datetime
 import difflib
@@ -231,7 +229,7 @@ def get_regexs():
 def main():
     regexs = get_regexs()
     refs = get_refs()
-    filenames = get_files(refs.keys())
+    filenames = get_files(list(refs.keys()))
 
     for filename in filenames:
         if not file_passes(filename, refs, regexs):

hack/boilerplate/boilerplate_test.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2016 The Kubernetes Authors.
 #
@@ -48,5 +48,5 @@ class TestBoilerplate(unittest.TestCase):
 
     sys.stdout = old_stdout
 
-    self.assertEquals(
+    self.assertEqual(
         output, ['././fail.go', '././fail.py'])

hack/boilerplate/test/fail.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2015 The Kubernetes Authors.
 #

hack/boilerplate/test/pass.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2015 The Kubernetes Authors.
 #