tests: handle unicode charactes in cli output

Type: fix

Change-Id: Ic4fb53e6d10a1de155a3088be81d53d9efeb0c0f
Signed-off-by: Klement Sekera <ksekera@cisco.com>
(cherry picked from commit 6be55648334308d4eaa4a02143b968720bb62078)

test/vpp_papi_provider.py

@@ -362,7 +362,8 @@ class VppPapiProvider(object):
         :param cli: CLI to execute
         :returns: CLI output
         """
-        return cli + "\n" + str(self.cli(cli))
+        return cli + "\n" + self.cli(cli).encode('ascii',
+                                                 errors='backslashreplace')
 
     def want_ip4_arp_events(self, enable_disable=1, ip="0.0.0.0"):
         return self.api(self.papi.want_ip4_arp_events,