Python regex to convert non-ascii characters in a string to closest ascii equivalents

I'm seeking simple Python function that takes a string and returns a similar one but with all non-ascii characters converted to their closest ascii equivalent. For example, diacritics and whatnot should be dropped. I'm imagining there must be a pretty canonical way to do this and there are plenty of related stackoverflow questions but I'm not finding a simple answer so it seemed worth a separate question.

Example input/output:

"Étienne" -> "Etienne"