[enh] revert logic for python3 for support of v11+ versions

templates/fetch_repos

-{% if odoo_version == '12.0' or odoo_version == '11.0' %}
-#!/usr/bin/env python3
-{% else %}
+{% if odoo_version == '10.0' %}
 #!/usr/bin/env python
+{% else %}
+#!/usr/bin/env python3
 {% endif %}
 # -*- coding: utf-8 -*-
 import grp

templates/fetch_repos_addons

-{% if odoo_version == '12.0' or odoo_version == '11.0' %}
-#!/usr/bin/env python3
-{% else %}
+{% if odoo_version == '10.0' %}
 #!/usr/bin/env python
+{% else %}
+#!/usr/bin/env python3
 {% endif %}
 # -*- coding: utf-8 -*-
 import grp
@@ -9,10 +9,10 @@ import os
 import pwd
 import shutil
 from subprocess import call
-{% if odoo_version == '12.0' or odoo_version == '11.0' %}
-from urllib.parse import urlsplit
-{% else %}
+{% if odoo_version == '10.0' %}
 from urlparse import urlsplit
+{% else %}
+from urllib.parse import urlsplit
 {% endif %}
 import yaml