In python3, the standard out data returned by
subprocess.Popen.communicate() will in most cases be bytes rather than a
string and must therefore be decoded.
Without this fix we hit the following error:
TypeError: a bytes-like object is required, not 'str'
Change-Id: I6d75f867ebfdb925970c3397175214b9050d7632
Closes-Bug: #1694463