[Ammako]

You just can't query by name anymore. You'll have to iterate through all your buffs in a loop and check each of their names until it finds the one you're looking for, by checking their names one by one.

Example from wowpedia:

for i=1,40 do
    local name, icon, _, _, _, etime = UnitBuff("player",i)
    if name == "Summon Chauffeur" or name == "Ban-Lu, Grandmaster's Companion" then
        --do things
    end
end

btw: https://wow.gamepedia.com/Patch_8.0.1/API_changes
Not a complete list, but it has a bunch of stuff.