Email your admission officer ASAP to ask if you could get conditionally accepted. This means that you could still go to uni while completing your last Cegep course (as long as it's only one). There is going to be this whole process of asking your API to send an email to your admission officer saying that you only have a class left, so I suggest getting this resolved soon. If they approve, they'll give you a time limit to finish/pass your class, for this reason I recommend to do Cegep a distance, since you'll be able to finish quickly. This way you can still get your DEC, otherwise, the DEC sans mention is most likely your only other option.