Catch KeyError instead of AttributeError in TaskManager when unknown task comes.
Catch KeyError instead of AttributeError in TaskManager when unknown task comes.

release-engineering/kobo,release-engineering/kobo,release-engineering/kobo,pombredanne/https-git.fedorahosted.org-git-kobo,pombredanne/https-git.fedorahosted.org-git-kobo,pombredanne/https-git.fedorahosted.org-git-kobo,pombredanne/https-git.fedorahosted.org-git-kobo,release-engineering/kobo