Require python3 in code

lib/trellis/plugins/vars/version.py

@@ -2,7 +2,7 @@
 from ansible.errors import AnsibleError
 from distutils.version import LooseVersion
 from operator import eq, ge, gt
-from sys import version_info
+from platform import python_version, python_version_tuple
 
 try:
     from __main__ import display
@@ -13,6 +13,11 @@
 version_requirement = '2.10.0'
 version_tested_max = '2.10.16'
 
+if python_version_tuple()[0] == '2':
+    raise AnsibleError(('Trellis no longer supports Python 2 (you are using version {}).'
+                        ' Python 2 reached end of life in 2020 and is unmaintained.\n'
+                        'Python 3 is required as of Trellis version v1.15.0.').format(python_version()))
+
 if not ge(LooseVersion(__version__), LooseVersion(version_requirement)):
     raise AnsibleError(('Trellis no longer supports Ansible {}.\n'
         'Please upgrade to Ansible {} or higher.').format(__version__, version_requirement))