Title: #4936: ipatests: Add compatibility against python-cryptography 3.0
The recently released python-cryptography 3.0 has backward incompatible
changes. One of them \[0\] breaks FreeIPA self-tests.
Note: this requires python-cryptography 2.7+.
To pull the PR as Git branch:
git remote add ghfreeipa https://github.com/freeipa/freeipa
git fetch ghfreeipa pull/4936/head:pr4936
git checkout pr4936