[WIP] ONOS-8091 Port python script and utilities to python3

Steps performed so far:
- Updated bash scripts and similar to explicitly invoke python3 (instead of python)
- Updated all python scripts using 2to3

Testing these changes will be a major headache because:
- different scripts are executed in different environments
  (e.g., Jenkins, cell servers, tutorial VMs, etc.)
- we don’t have control on all environments
- some environments we used to control have been dismissed
  (e.g., cell servers)

The approach for now is to focus on the essentials:
- Jenkins jobs for pre-merge and release

Test and fix everything else as the need arises.

Change-Id: I943e214760c9dea9a7ded0d47ef08adbc0ed0bec
diff --git a/tools/test/scenarios/bin/check-dhcp-netcfg.py b/tools/test/scenarios/bin/check-dhcp-netcfg.py
index c828c84..2786785 100755
--- a/tools/test/scenarios/bin/check-dhcp-netcfg.py
+++ b/tools/test/scenarios/bin/check-dhcp-netcfg.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 import requests
 import sys
@@ -6,7 +6,7 @@
 from requests.auth import HTTPBasicAuth
 
 if len(sys.argv) < 3:
-    print "usage: find-dhcp-netcfg onos-node name1=value1 ..."
+    print("usage: find-dhcp-netcfg onos-node name1=value1 ...")
     sys.exit(1)
 
 node = sys.argv[1]
@@ -15,7 +15,7 @@
                           ':8181/onos/v1/network/configuration/apps/org.onosproject.dhcp',
                           auth=HTTPBasicAuth('onos', 'rocks'))
 
-print cfgRequest.text
+print(cfgRequest.text)
 
 if cfgRequest.status_code != 200:
     sys.exit(1)
@@ -32,8 +32,8 @@
     value = pair[1]
 
     if dhcp[name] != value:
-        print name + " differs: expected " + value + " but found " + dhcp[name]
-        print cfgJson
+        print(name + " differs: expected " + value + " but found " + dhcp[name])
+        print(cfgJson)
         sys.exit(1)