Extra spaces in border with show_signs = true and specific sign characters

[cultab]

First with the character 

Then with the character a

Works as expected with show_signs = false

[codingjerk]

Same with any non-ascii characters in diagnostic messages.

There are examples of diagnostics where leading non breaking space breaks the border:

Replacing every nbsp with dot with:

format = function(diagnostic)
    return diagnostic.message:gsub(" ", ".")
end,

renders well:

update: the non-ascii character doesn't have to be leading character. If occur anywhere in the line it breaks the border on that line