% ipa trust-add ad.test --type=asdf
ipa: ERROR: invalid 'type': must be one of (u'ad',)

The message above comes from StrEnum() validator which is common one for
all StrEnum()s. I made a ValidationError in execute() method to catch up
any discrepancies when other types of trust will be added as Python
doesn't have 'case/switch' so you are left alone with 'if' or list-based
lambdas which don't look so clear.

What we probably want to add is more friendly way to display these
StrEnum values, dropping u'' and simply showing proper unicode as we do
for help already.