Comment 4 for bug 1805327

Using apt for the comparison and checking for a value of '1' ensures the stepped upgrade approach thus enforcing the upgrade policy:

>>> apt.version_compare('queens', 'mitaka')
4
>>> apt.version_compare('pike', 'mitaka')
3
>>> apt.version_compare('ocata', 'mitaka')
2
>>> apt.version_compare('newton', 'mitaka')
1

This may have been by design but it feels a little brittle.