(add-after 'patch-shebangs 'use-absolute-python
           (lambda* (#:key inputs outputs #:allow-other-keys)
             (substitute* (string-append (assoc-ref outputs "out")
                                         "/share/gtags/script/pygments_parser.py")
               (("#!/usr/bin/env python")
                (string-append "#!" (assoc-ref inputs "python")
                               "/bin/python3")))))