New versions of pyxel only works with recent version of SDL2
Hi,

I have been struggling with this for quite a while, and I guess this could maybe help others. Maybe it could be included in the documentation?

I'm currently running Linux Mint 20.2 and my SDL2 version is 2.0.10
Only the old versions of pyxel, versions 1.9.7 and older can work. Versions 1.9.8 and more recent updates will raise an error while importing the library:

`ImportError: /usr/local/lib/python3.8/dist-packages/pyxel/pyxel_extension.abi3.so: undefined symbol: SDL_Metal_DestroyView`

To make it work you have to update your SDL2 to at least 2.0.12 
With LM 20.2 I cannot do that directly by just updating with apt. I found this thread giving a workaround:
https://github.com/TerryCavanagh/VVVVVV/issues/618#issuecomment-968338212


This is not actually a bug, but I'm posting it here in case someone is also struggling with this.