Replying to @jhpalmieri:

Many spkg-check.in and spkg-install.in files contain

if [ -z "$SAGE_LOCAL" ]; then
    echo >&2 "Error: SAGE_LOCAL undefined - exiting..."
    echo >&2 "Maybe run 'sage -sh'?"
    exit 1
fi

Should these lines just be deleted?

Yes -- they are outdated

(from #29488)

CC: @jhpalmieri @embray

Component: build

Author: John Palmieri

Branch/Commit: 251ab47

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/29492