What kind of action is it to use a spell scroll?

@JeremyECrawford p139 and p200 of DMG contradict each other. What action is it to use a spell scroll. 139 says action, 200 says spell based.

— boolslice (@boolslice) August 4, 2016

Using a spell scroll requires the spell's casting time (specific beats general). #DnD https://t.co/Bx2yqgilas

— Jeremy Crawford (@JeremyECrawford) August 4, 2016

@NoahTopper @boolsliceDoes that mean you can use some scrolls as a reaction? Yes.

— Jeremy Crawford (@JeremyECrawford) August 4, 2016