#24014 deprecated the PIP_INSTALL environment variable in favor of the sdh_pip_install helper function. This ticket is to remove PIP_INSTALL entirely.

CC: @slel @tscrim @embray @jdemeyer

Component: build

Keywords: pip

Author: Frédéric Chapoton

Branch/Commit: ef11f05

Reviewer: Erik Bray

Issue created by migration from https://trac.sagemath.org/ticket/24018