Wow, had quite a time reading all the responses to this. After my initial post on this and looking at the video a couple more times, I might be changing my point of view on this, so Magnatom, take this for what it's worth!
1. When Magnatom was just about to exit the roundabout, it looks like he was not in primary position relative to the kerb (can't tell 100% from the video, but it looks like that). That would seem to allow adequate room for the driver to overtake (again, hard to tell, it just seems from the video there was).
2. Then I'm not sure Magnatom did an adequate shoulder check or had time to confirm he could overtake to the right of the manhole cover.
3. Even if it is legal, I'm not sure it's a good idea to (on a bicycle that is) to overtake another road user (unless I had to) exiting a roundabout, and double that up with the manhole cover being a further hazard. Too much depending on the driver behind you.
Having said all that, I do still stand by the fact the driver wasn't driving well and appeared to be impatient; I know if I saw a cyclist exiting a roundabout with a slower cyclist in front as well as a manhole cover on the road, I'd be in absolutely no hurry to overtake at that point.
What doesn't come across from the video is how abruptly or not Magnatom swung out (if he did), or the speed of the car (could that driver has braked to avoid overtaking or was he committed by then and surprized by Magnatom overtaking?).
But I think to avoid this situation, usually I wouldn't overtake another road user exiting a roundabout -the problems are that road positioning isn't 100% defined or sorted out at that point, and motorized vehicles are tending to accelerate after encountering the roundabout. I'd wait until traffic and road layout becomes more consistent and predictable.