It eases backporting in iruya and hunter as a few logs can't be
decoded as ascii [1].
[1] https://build.opnfv.org/ci/job/functest-opnfv-functest-vnf-iruya-juju_epc-run/56/console
Change-Id: If241c5323f286c33aaae804479375efe4c3c1588
Signed-off-by: Cédric Ollivier <ollivier.cedric@gmail.com>
 
         process = subprocess.Popen(cmd_line, stdout=subprocess.PIPE,
                                    stderr=subprocess.STDOUT)
-        output = process.stdout.read().decode()
+        output = process.stdout.read().decode("utf-8")
         if ('Error loading client' in output or
                 'Unexpected error' in output):
             raise Exception(output)