Fix tests with Python 3.10

<div id="comment:0"></div>

Assorted Python 3.10 test fixes. See individual commit messages for details.

Component: **packages: standard**

Author: **Antonio Rojas**

Branch/Commit: **[`2f13b86`](https://github.com/sagemath/sagetrac-mirror/commit/2f13b8666aef7001b7464f7cf68d145a5752c067)**

Reviewer: **Matthias Koeppe**

_Issue created by migration from https://trac.sagemath.org/ticket/33013_

