tests: cli wrapper should return string

Python3 fixes.

Type: fix
Signed-off-by: Ole Troan <ot@cisco.com>
Change-Id: I648b2142d45dfab9146a02eeb1b12de11103ff9f
Signed-off-by: Ole Troan <ot@cisco.com>

test/test_ip4.py

@@ -100,7 +100,7 @@ class TestIPv4(VppTestCase):
         :param int packet_size: Required packet size.
         :param Scapy pkt: Packet to be modified.
         """
-        dst_if_idx = packet_size / 10 % 2
+        dst_if_idx = int(packet_size / 10 % 2)
         dst_if = self.flows[src_if][dst_if_idx]
         info = self.create_packet_info(src_if, dst_if)
         payload = self.info_to_payload(info)
@@ -377,7 +377,7 @@ class TestICMPEcho(VppTestCase):
 
         icmp_id = 0xb
         icmp_seq = 5
-        icmp_load = '\x0a' * 18
+        icmp_load = b'\x0a' * 18
         p_echo_request = (Ether(src=self.pg0.remote_mac,
                                 dst=self.pg0.local_mac) /
                           IP(src=self.pg0.remote_ip4, dst=self.pg0.local_ip4) /
@@ -1938,7 +1938,7 @@ class TestIPv4Frag(VppTestCase):
         packets = self.dst_if.get_capture(3)
 
         # Assume VPP sends the fragments in order
-        payload = ''
+        payload = b''
         for p in packets:
             payload_offset = p.frag * 8
             if payload_offset > 0: