Why Am I Getting AttributeError: Module 'enum' Has No Attribute 'IntFlag' in Ansible Tower?

Issue

When running a project update in AnsibleTower, it fails with the error:

Error example:

Identity added: /tmp/awx_1081_472f7ttm/artifacts/1081/ssh_key_data (foobar@example.com)
Traceback (most recent call last):
  File "/usr/local/bin/ansible-playbook", line 30, in <module>
    import shutil
  File "/usr/lib64/python3.6/shutil.py", line 10, in <module>
    import fnmatch
  File "/usr/lib64/python3.6/fnmatch.py", line 14, in <module>
    import re
  File "/usr/lib64/python3.6/re.py", line 142, in <module>
    class RegexFlag(enum.IntFlag):
AttributeError: module 'enum' has no attribute 'IntFlag'