Impossible to remove or view members with question marks in the email address

A bulk import from a file that had a stray ? in it caused someone to be subscribed akin to first.last?@example.com

While postorious correctly makes that %3F in the URLs, it generates a 404 from the DELETE request in the underlying API:

DELETE http://10.10.10.10:8001/3.0/lists/my-list.lists.example.com/member/first.last?@example.com [404]

And indeed, https://lists.example.com/mailman3/postorius/lists/my-list.lists.example.com/members/options/first.last%3F@example.com throws up a 404 as well.

Sadly this 404 is surfaced to the admin trying to manage things as a bare 500, which made diagnosis difficult.