> The solution is to patch Python to refer to our ‘sh’ instead of /bin/sh
> (as is done for Guile’s ice-9/popen.scm).

> Can you do that?

I changed 'arguments', but 'gobject-introspection' failed with the same
error.

python.scm:

    (arguments `(#:tests? #f ; XXX: some tests fail
                 #:phases (alist-cons-before
                           'configure 'pre-configure
                           (lambda* (#:key inputs #:allow-other-keys)
                             (let ((bash (assoc-ref inputs "bash")))
                               (substitute* "Lib/subprocess.py"
                                 (("/bin/sh")
                                  (string-append bash "/bin/bash")))))
                           %standard-phases)))

subprocess.py:

            if shell:
                args = ["/nix/store/4mg8b8vvmava68y64qmm70gqfnhhjzmx-bash-4.2/bin/bash", "-c"] + args
                if executable:
                    args[0] = executable