When the default principal already exists on a host with the ipa server already installed the command:
sudo ipsilon-server-install --ipa=yes --info-sssd=yes --form=yes

fails with the following error:

a bytes-like object is required, not 'str'

which is being generated from here: https://pagure.io/ipsilon/blob/master/f/ipsilon/helpers/ipa.py#_106

I think the output of the exception is malformed or not what we expect.