Upgrading Blender add-ons from 2.79 to 2.80, part 2

In the first part of this series on porting add-ons from 2.79 to 2.80 I promised to keep notes on issues that might pop-up so here is my second batch:

• scene.objects.active is no longer available. Use context.active_object. This is due to working with collections,
• no bl_category, so you cannot decide where your Panel will be located in the Toolbar. This is too bad, but maybe I don understand this completely,
• the bgl module does not support direct mode at all (not even as an option). This hurts really bad. Yes the new , modern OpenGL capabilities are what we all wished for but porting the old stuff to the new is far from trivial,
• BVHTree.FromObject() expects a Depsgraph not a scene. This is a breaking change. The relevant Depsgraph is available from context.depsgraph,
• scene.ray_cast() expects a view_layer to determine what is visible in the scene. Again a breaking change related to the previous one. The relevant view_layer is available from context.window.view_layer,
• Lamps are now called Lights, this affects object.type ('LIGHT') as well as bpy.data.lights,
• Color() constructor always expects 3 values, but the .color attribute in a vertex color layer is 4 items (RGBA). Like the next item on this list this might have been present in 2.79 already but just comes to light now that I am porting add-ons,
• The name of a module may not contain -  (i.e. a dash or minus sign) or install will silently fail (might have been the case in 2.79 too)