Migrate cvp-sanity to Python3

* use print function from future
* convert dict keys and values to list
* do not use bunch imports
* fix requirements mismatch
Related: PROD-33849

Change-Id: Ifecc3a9dcdcfe3243f7dcf2c709a80e9a7c765a1
diff --git a/test_set/cvp-sanity/tests/test_default_gateway.py b/test_set/cvp-sanity/tests/test_default_gateway.py
index 259abba..31c2447 100644
--- a/test_set/cvp-sanity/tests/test_default_gateway.py
+++ b/test_set/cvp-sanity/tests/test_default_gateway.py
@@ -12,7 +12,7 @@
 
     gateways = {}
 
-    for node in netstat_info.keys():
+    for node in list(netstat_info.keys()):
         gateway = netstat_info[node]
         if isinstance(gateway, bool):
             gateway = 'Cannot access node(-s)'
@@ -21,7 +21,7 @@
         else:
             gateways[gateway].append(node)
 
-    assert len(gateways.keys()) == 1, (
+    assert len(list(gateways.keys())) == 1, (
         "There is a problem with default gateway for '{}' group of nodes:\n"
         "{}".format(group, json.dumps(gateways, indent=4))
     )