[SDFAB-1197] First stab to update ONOS to py3

Update has been performed only on the scripts and the
executables strictly necessary for the following use cases:

- Build (including Intellij)
- Tests (including Intellij)
- Docker build (including dev and yourkit)
- Upload snapshot (including local)
- Release

Finally, fix the ability to run ONOS using onos-local targets,
stc and docker stc (aka up4 stc env). Last but not least, updated
the azul image to a newer one which exports also the PYTHONENCODING

Change-Id: Ie96f3a9c76dbba83b1fc3896a372f1045d3d7ccc
diff --git a/tools/build/bazel/pom_generator.py b/tools/build/bazel/pom_generator.py
index 2e16f49..1ad54ec 100755
--- a/tools/build/bazel/pom_generator.py
+++ b/tools/build/bazel/pom_generator.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """
  Copyright 2018-present Open Networking Foundation
 
@@ -49,7 +49,7 @@
         with open(name, "w") as file:
             file.write(msg)
     else:
-        print msg
+        print(msg)
 
 
 def write_pom(output, coords, deps):
@@ -70,7 +70,7 @@
     import sys
 
     if len(sys.argv) < 3:
-        print 'usage: pom_generator pom.xml maven_coords dep_coords1 dep_coords2 ...'
+        print('usage: pom_generator pom.xml maven_coords dep_coords1 dep_coords2 ...')
         sys.exit(1)
 
     output = sys.argv[1]