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

[Arun Isaac <arunisaac@systemreboot.net>]

I'm working on fixing this bug. I have modified
guix/build/python-build-system.scm for the same. In particular, I have
added #:use-module (guix packages) because I need the functions
`package-name' and `package-transitive-target-inputs'. But, when I try
building any python-build-system package with something like
"./pre-inst-env guix build scons", I get a ("no code for module" (guix
packages)) error. What am I missing?

Full backtrace follows:

Backtrace:
In ice-9/eval.scm:
 432: 19 [eval # ()]
In system/base/compile.scm:
 152: 18 [compile-file "/gnu/store/38rxls2y8v8zjva7xq7zv99rv6c81bq3-module-import/guix/build/python-build-system.scm" ...]
  43: 17 [call-once #<procedure ae84c0 at system/base/compile.scm:56:5 ()>]
In ice-9/boot-9.scm:
 174: 16 [with-throw-handler #t ...]
In system/base/compile.scm:
  59: 15 [#<procedure ae8480 at system/base/compile.scm:58:9 ()>]
 155: 14 [#<procedure ae8500 at system/base/compile.scm:153:8 (port)> #<closed: file 0>]
 218: 13 [read-and-compile #<input: /gnu/store/38rxls2y8v8zjva7xq7zv99rv6c81bq3-module-import/guix/build/python-build-system.scm 6> ...]
 234: 12 [lp () #f #<module (#{ g152}#) ae7a20>]
 182: 11 [lp (#<procedure compile-tree-il (x e opts)>) (define-module # # ...) ...]
In ice-9/boot-9.scm:
2404: 10 [save-module-excursion #<procedure c967e0 at language/scheme/compile-tree-il.scm:29:3 ()>]
In language/scheme/compile-tree-il.scm:
  31: 9 [#<procedure c967e0 at language/scheme/compile-tree-il.scm:29:3 ()>]
In ice-9/psyntax.scm:
1106: 8 [expand-top-sequence ((define-module # # # ...)) () ((top)) ...]
 989: 7 [scan ((define-module # # # ...)) () ((top)) ...]
 279: 6 [scan ((#(syntax-object let # ...) (#) (# #) ...)) () ...]
In ice-9/eval.scm:
 411: 5 [eval # ()]
In ice-9/boot-9.scm:
2954: 4 [define-module* (guix build python-build-system) #:filename ...]
2929: 3 [resolve-imports ((# # gnu:) (#) (#) (#) ...)]
2870: 2 [resolve-interface (guix packages) #:select ...]
In unknown file:
   ?: 1 [scm-error misc-error #f "~A ~S" ("no code for module" (guix packages)) #f]
In ice-9/boot-9.scm:
 109: 0 [#<procedure ae8440 at ice-9/boot-9.scm:100:6 (thrown-k . args)> misc-error ...]

ice-9/boot-9.scm:109:20: In procedure #<procedure ae8440 at ice-9/boot-9.scm:100:6 (thrown-k . args)>:
ice-9/boot-9.scm:109:20: no code for module (guix packages)
builder for `/gnu/store/lsrxzd1hdsgpb9zhrdv02dsxihpmxmww-module-import-compiled.drv' failed with exit code 1
@ build-failed /gnu/store/lsrxzd1hdsgpb9zhrdv02dsxihpmxmww-module-import-compiled.drv - 1 builder for `/gnu/store/lsrxzd1hdsgpb9zhrdv02dsxihpmxmww-module-import-compiled.drv' failed with exit code 1
cannot build derivation `/gnu/store/pm2r6cbcfij8d7nzdxkzqx1dq880mhg8-scons-2.3.4.drv': 1 dependencies couldn't be built
guix build: error: build failed: build of `/gnu/store/pm2r6cbcfij8d7nzdxkzqx1dq880mhg8-scons-2.3.4.drv' failed