Fix exception for ipaddress in python2 (#1164)

The 'ipaddress.ip_interface' accepts only unicode str as input, which is
default in python3. However, an exception will raise when running in
python2. This commit fix the issue.

Signed-off-by: bingwang <bingwang@microsoft.com>

scripts/fast-reboot-dump.py

@@ -12,6 +12,7 @@
 import syslog
 import traceback
 import ipaddress
+from builtins import str #for unicode conversion in python2
 
 
 ARP_CHUNK = binascii.unhexlify('08060001080006040001') # defines a part of the packet for ARP Request
@@ -39,7 +40,7 @@ def generate_neighbor_entries(filename, all_available_macs):
         arp_output.append(obj)
 
         ip_addr = key.split(':')[2]
-        if ipaddress.ip_interface(ip_addr).ip.version != 4:
+        if ipaddress.ip_interface(str(ip_addr)).ip.version != 4:
             #This is ipv6 address
             ip_addr = key.replace(key.split(':')[0] + ':' + key.split(':')[1] + ':', '')
         neighbor_entries.append((vlan_name, mac, ip_addr))
@@ -232,7 +233,7 @@ def send_garp_nd(neighbor_entries, map_mac_ip_per_vlan):
     # send arp/ndp packets
     for vlan_name, dst_mac, dst_ip in neighbor_entries:
         src_if = map_mac_ip_per_vlan[vlan_name][dst_mac]
-        if ipaddress.ip_interface(dst_ip).ip.version == 4:
+        if ipaddress.ip_interface(str(dst_ip)).ip.version == 4:
             send_arp(sockets[src_if], src_mac_addrs[src_if], src_ip_addrs[vlan_name], dst_mac, dst_ip)
         else:
             send_ndp(sockets[src_if], src_mac_addrs[src_if], src_ip_addrs[vlan_name], dst_mac, dst_ip)