devmode-test: fix running with Python 3

Use a syntax that works with both versions.

BUG=chromium:998225
TEST=devinstall_test.py passes w/python->python3

Change-Id: Ic54de5418b88cd837ef7469b1431be5374605bad
Reviewed-on: https://chromium-review.googlesource.com/1799784
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
diff --git a/devmode-test/devinstall_test.py b/devmode-test/devinstall_test.py
index cd5f027..97512a1 100755
--- a/devmode-test/devinstall_test.py
+++ b/devmode-test/devinstall_test.py
@@ -151,7 +151,7 @@
       # crbug.com/955147: /usr/local/bin/python symlink doesn't exist.
       # Use python-wrapper instead.
       self.device.RunCommand(['sudo', '-u', 'chronos', '--', 'python-wrapper',
-                              '-c', '"print \'hello world\'"'])
+                              '-c', '"print(\'hello world\')"'])
     except (cros_build_lib.RunCommandError,
             remote_access.SSHConnectionError) as e:
       self.devserver.PrintLog()