The list/help mechanisms do not cope well with empty collection modules (eg touch whatever.py; inv -c whatever -l). Fix this.
touch whatever.py; inv -c whatever -l
Also related, I don't think we used to raise raw CollectionNotFound when tasks files could not be found, make sure that's not also broken.
I see nothing about that 2nd bit so it's probably its own issue. See #149.
Failing test proving #145
Fix #145 by printing useful error on empty collections
Changelog re #145