No confirmation for the cast presence at Calgary at the moment though.
"No other guests have been confirmed for the galas yet, but executive director Steve Schroeder says the festival has invited I Saw The Light cast and writer-director Marc Abraham for the opening gala."
http://www.rodeocountryradio.com/country-news/2015/8/18/hank-williams-biopic-i-saw-the-light-to-open-calgary-international-film-festival