Output of awesome --version:

awesome v4.3 (Too long)
• Compiled against Lua 5.3.6 (running with Lua 5.3)
• D-Bus support: ✔
• execinfo support: ✔
• xcb-randr version: 1.6
• LGI version: 0.9.2

How to reproduce the issue:

1. Create a timer with

gears.timer {
    timeout = 2,
    autostart = true,
    callback = function()
        test()
    end,
    single_shot = true
}

2. In the test() callback add error()
   Example:

local function test()
    naughty.notify({ text = "One" })
    naughty.notify({ text = "Two" })
    error("give error")
end

Actual result:

The callback keeps going without stopping and no error is given.

Expected result:

It should only run once, give an error and stop.