Spelling errors not visible

[mkalinski]

Regardless of theme, :set spell does not visually mark spelling mistakes in any way, while it does correctly in terminal neovim for the same themes.

Mappings related to spelling, like ]s, still work though.

[mkalinski]

After playing around with color themes, this seems to only affect ones which are not written specifically for GUI. Still, terminal neovim handles both cases correctly, even with set termguicolors.

[mkalinski]

After investigating some more: the issue seems to be that pynvim is unable to display any form of underline for text (which is usually used for spelling errors).