extract_kernel: make it py2/py3 compatible

use py3 for AOSP build, while the script itself can be
executed under py2/py3 environment directly.

TEST: extract info from Pixel 4 kernel

Change-Id: I00db6dabb1ff93f0758017a666c476816caefae7
diff --git a/tools/test_extract_kernel.py b/tools/test_extract_kernel.py
index 1a1cfcb..002e387 100644
--- a/tools/test_extract_kernel.py
+++ b/tools/test_extract_kernel.py
@@ -15,16 +15,16 @@
 # limitations under the License.
 
 import unittest
-from extract_kernel import get_version, dump_version
+from extract_kernel import dump_version
 
 class ExtractKernelTest(unittest.TestCase):
   def test_extract_version(self):
-    self.assertEqual("4.9.100", get_version(
-        b'Linux version 4.9.100-a123 (a@a) (a) a\n\x00', 0))
-    self.assertEqual("4.9.123", get_version(
-        b'Linux version 4.9.123 (@) () \n\x00', 0))
+    self.assertEqual("4.9.100", dump_version(
+        b'Linux version 4.9.100-a123 (a@a) (a) a\n\x00'))
+    self.assertEqual("4.9.123", dump_version(
+        b'Linux version 4.9.123 (@) () \n\x00'))
 
   def test_dump_self(self):
     self.assertEqual("4.9.1", dump_version(
         b"trash\x00Linux version 4.8.8\x00trash\x00"
-        "other trash Linux version 4.9.1-g3 (2@s) (2) a\n\x00"))
+        b"other trash Linux version 4.9.1-g3 (2@s) (2) a\n\x00"))