Wait a few weeks to see if your mate actually failed the class. If he passed, no problem and you'll be glad you didn't make a big deal out of it. If he failed and can't go on the trip, then you'll have to make the call, but I'd go on the trip. Don't let other people control your destiny, especially when they appear to be trying to hold you back from something just because they can't do it.
Touring with a partner is fun. Touring solo is also fun. I've done both and met many wonderful people while doing so. Ride without guilt no matter how this plays out. Also, there must be a week or two somewhere over the next year or so when you can do a shorter tour with your roommate. Make it happen if you can.
I did have one occasion on a tour where I wanted to go my separate way from a touring partner. Unfortunately, it was the first long trip my wife and I took on our first tandem, so I had to shut down my childish tantrum and get on with it. I think I was just hungry and tired, but my memory isn't what it used to be. That was twenty-seven years ago and we've ridden many hundreds of thousands of miles together since.