Enable running unit test and coverage in py3.

- Migrate run_tests.sh to python3
- Running run_tests.sh in py2 is not supported.

Bug: 157392770
Test: ./run_test.sh
./run_test_py2.sh
atest --host acloud_test
atest --host acloud_test_py3

Change-Id: Ibf6a535f36c9ebd196b075eed092c10992f338eb
diff --git a/setup/setup_common_test.py b/setup/setup_common_test.py
index e17e529..5a00cfc 100644
--- a/setup/setup_common_test.py
+++ b/setup/setup_common_test.py
@@ -14,7 +14,6 @@
 """Tests for host_setup_runner."""
 import subprocess
 import unittest
-from six import b
 
 from acloud import errors
 from acloud.internal.lib import driver_test_lib
@@ -23,21 +22,21 @@
 
 class SetupCommonTest(driver_test_lib.BaseDriverTest):
     """Test HostPkgTaskRunner."""
-    PKG_INFO_INSTALLED = b("""fake_pkg:
+    PKG_INFO_INSTALLED = """fake_pkg:
   Installed: 0.7
   Candidate: 0.7
   Version table:
-""")
-    PKG_INFO_NONE_INSTALL = b("""fake_pkg:
+"""
+    PKG_INFO_NONE_INSTALL = """fake_pkg:
   Installed: (none)
   Candidate: 0.7
   Version table:
-""")
-    PKG_INFO_OLD_VERSION = b("""fake_pkg:
+"""
+    PKG_INFO_OLD_VERSION = """fake_pkg:
   Installed: 0.2
   Candidate: 0.7
   Version table:
-""")
+"""
 
     # pylint: disable=invalid-name
     def testPackageNotInstalled(self):