(from #32372 comment:10)

This fixes the problem on ubuntu-trusty-standard (https://github.com/mkoeppe/sage/runs/4128487418?check_suite_focus=true), which fails to download from upstream_url that points to pypi.io

CC: @fchapoton @slel @sagetrac-tmonteil @jhpalmieri @kliem

Component: build

Author: Matthias Koeppe

Branch/Commit: 48b7927

Reviewer: Jonathan Kliem

Issue created by migration from https://trac.sagemath.org/ticket/32405