bug#25235: Wrapped python programs get native-inputs in PYTHONPATH

[Arun Isaac]

> How does it look?

I tried your patch. But native-inputs are still there in the wrapped
PYTHONPATH. I printed out the results from various steps from the wrap
phase. They are as follows:

`build-time-inputs' is

("/gnu/store/5wbi6vsi12bmpzygwhys3c0cc6sjdw40-python-beautifulsoup4-4.5.3"
"/gnu/store/kc5gl1j85y9ispjsgbg5f5c6jdy1k32s-python-flask-0.11.1"
"/gnu/store/3ib43rpca6qzwfcav8s9ivm3dikpxq87-python-mock-1.0.1"
"/gnu/store/6q4hszis7z6x44ig2zlwjwlcjy3vvfmp-python-mpd2-0.5.5"
"/gnu/store/5wx6yffx6dppd2dr91qfi1jlpqlp9f5m-python-nose-1.3.7"
"/gnu/store/kqjfgfwzm7sq43fnng1w23mjyr2xrd75-python-pathlib-1.0.1"
"/gnu/store/b9yn8bfd43pvrp2wyinf6rf2qw113r5p-python-pyxdg-0.25"
"/gnu/store/g4vfl4wy81y14fjhlpmgqh0i01cg37mb-python-pylast-1.6.0"
"/gnu/store/nim5r75b1kzawln3a1bgag2f12vdmb8x-python-rarfile-2.8"
"/gnu/store/wbaaacm1m7bzbhi3z3scwbz2p4pf2ybg-python-responses-0.5.1")

`path' is

("/gnu/store/5wbi6vsi12bmpzygwhys3c0cc6sjdw40-python-beautifulsoup4-4.5.3/lib/python3.5/site-packages"
"/gnu/store/r3f04sda4gh5vbsa7zb5x0ygf326cp75-python-flask-0.11.1/lib/python3.5/site-packages"
"/gnu/store/3ib43rpca6qzwfcav8s9ivm3dikpxq87-python-mock-1.0.1/lib/python3.5/site-packages"
"/gnu/store/5mkb6im3dijkw4f5146mjz4c49qgcklq-python-mpd2-0.5.5/lib/python3.5/site-packages"
"/gnu/store/9z450rcsza3x448ky83fkd5636ck9aqd-python-nose-1.3.7/lib/python3.5/site-packages"
"/gnu/store/kqjfgfwzm7sq43fnng1w23mjyr2xrd75-python-pathlib-1.0.1/lib/python3.5/site-packages"
"/gnu/store/b9yn8bfd43pvrp2wyinf6rf2qw113r5p-python-pyxdg-0.25/lib/python3.5/site-packages"
"/gnu/store/g4vfl4wy81y14fjhlpmgqh0i01cg37mb-python-pylast-1.6.0/lib/python3.5/site-packages"
"/gnu/store/nim5r75b1kzawln3a1bgag2f12vdmb8x-python-rarfile-2.8/lib/python3.5/site-packages"
"/gnu/store/wbaaacm1m7bzbhi3z3scwbz2p4pf2ybg-python-responses-0.5.1/lib/python3.5/site-packages"
"/gnu/store/m6ir6mj7laxcwsjrz0lvxm7q04w0anhp-python-discogs-client-2.2.1/lib/python3.5/site-packages"
"/gnu/store/v3xiyw0cj08qmpn08jaiznd8ak3nvdga-python-jellyfish-0.5.6/lib/python3.5/site-packages"
"/gnu/store/pwxvvi24950x6rgvl4f46z89sbpa2b7a-python-munkres-1.0.8/lib/python3.5/site-packages"
"/gnu/store/nws3867b5q78ri461wr3rdwgqzasvv2a-python-musicbrainzngs-0.6/lib/python3.5/site-packages"
"/gnu/store/wsw2nr30nhz29dww1hfjb6lgqn2ckrgy-python-mutagen-1.36/lib/python3.5/site-packages"
"/gnu/store/n7fh268b1g1g87s4djvm672p2xmwkd5r-python-pyyaml-3.12/lib/python3.5/site-packages"
"/gnu/store/y3ncl6ia04vqdkhnhgzb3iabcsczj0zb-python-unidecode-0.04.20/lib/python3.5/site-packages"
"/gnu/store/alk9r3rir93pjmv8im20f8xrvv90219z-python-3.5.2/lib/python3.5/site-packages"
"/gnu/store/z2mmzglkykws7hc9k2sr40fidiv62cpa-python-werkzeug-0.11.15/lib/python3.5/site-packages"
"/gnu/store/5w60y9zyjskv179sf4pmq2kzpff887dv-python-click-6.7/lib/python3.5/site-packages"
"/gnu/store/f4qqgaql0f95alxrz9r52n3m5ahjrc1s-python-jinja2-2.8/lib/python3.5/site-packages"
"/gnu/store/n0l3szawn661n2rjk6nnbajzzc02pmfj-python-itsdangerous-0.24/lib/python3.5/site-packages"
"/gnu/store/rpnfm1v7vnwxl3wpbadz2bz25s2x1bbg-python-six-1.10.0/lib/python3.5/site-packages"
"/gnu/store/64ahrdmjmmm8id5327i5kqjj8ppvi2kl-python-cookies-2.2.1/lib/python3.5/site-packages"
"/gnu/store/2iyrxbr6k1qdcrhfpv3cz1nh1znwnga5-python-requests-2.13.0/lib/python3.5/site-packages"
"/gnu/store/0c28plwcf33lnibf27h8ijig467pphiw-python-oauthlib-1.0.3/lib/python3.5/site-packages"
"/gnu/store/m48bcrmrzrcb79p6dhaq0diwr3aacfq3-python-markupsafe-0.23/lib/python3.5/site-packages")

(remove build-time-dependency? path) is

("/gnu/store/r3f04sda4gh5vbsa7zb5x0ygf326cp75-python-flask-0.11.1/lib/python3.5/site-packages"
"/gnu/store/5mkb6im3dijkw4f5146mjz4c49qgcklq-python-mpd2-0.5.5/lib/python3.5/site-packages"
"/gnu/store/9z450rcsza3x448ky83fkd5636ck9aqd-python-nose-1.3.7/lib/python3.5/site-packages"
"/gnu/store/m6ir6mj7laxcwsjrz0lvxm7q04w0anhp-python-discogs-client-2.2.1/lib/python3.5/site-packages"
"/gnu/store/v3xiyw0cj08qmpn08jaiznd8ak3nvdga-python-jellyfish-0.5.6/lib/python3.5/site-packages"
"/gnu/store/pwxvvi24950x6rgvl4f46z89sbpa2b7a-python-munkres-1.0.8/lib/python3.5/site-packages"
"/gnu/store/nws3867b5q78ri461wr3rdwgqzasvv2a-python-musicbrainzngs-0.6/lib/python3.5/site-packages"
"/gnu/store/wsw2nr30nhz29dww1hfjb6lgqn2ckrgy-python-mutagen-1.36/lib/python3.5/site-packages"
"/gnu/store/n7fh268b1g1g87s4djvm672p2xmwkd5r-python-pyyaml-3.12/lib/python3.5/site-packages"
"/gnu/store/y3ncl6ia04vqdkhnhgzb3iabcsczj0zb-python-unidecode-0.04.20/lib/python3.5/site-packages"
"/gnu/store/alk9r3rir93pjmv8im20f8xrvv90219z-python-3.5.2/lib/python3.5/site-packages"
"/gnu/store/z2mmzglkykws7hc9k2sr40fidiv62cpa-python-werkzeug-0.11.15/lib/python3.5/site-packages"
"/gnu/store/5w60y9zyjskv179sf4pmq2kzpff887dv-python-click-6.7/lib/python3.5/site-packages"
"/gnu/store/f4qqgaql0f95alxrz9r52n3m5ahjrc1s-python-jinja2-2.8/lib/python3.5/site-packages"
"/gnu/store/n0l3szawn661n2rjk6nnbajzzc02pmfj-python-itsdangerous-0.24/lib/python3.5/site-packages"
"/gnu/store/rpnfm1v7vnwxl3wpbadz2bz25s2x1bbg-python-six-1.10.0/lib/python3.5/site-packages"
"/gnu/store/64ahrdmjmmm8id5327i5kqjj8ppvi2kl-python-cookies-2.2.1/lib/python3.5/site-packages"
"/gnu/store/2iyrxbr6k1qdcrhfpv3cz1nh1znwnga5-python-requests-2.13.0/lib/python3.5/site-packages"
"/gnu/store/0c28plwcf33lnibf27h8ijig467pphiw-python-oauthlib-1.0.3/lib/python3.5/site-packages"
"/gnu/store/m48bcrmrzrcb79p6dhaq0diwr3aacfq3-python-markupsafe-0.23/lib/python3.5/site-packages")

Somehow, the paths in `build-time-inputs' are not the same as those in
`path'. Notice the different hashes. Hence `remove' does not succeed in
filtering them out.

> +                       ;; TODO: Something like this:
> +                       ;; (disallowed-references native-inputs)

What is this part for?