manual: "python modules using pip in a virtualenv" example don't work

[davidak]

Issue description

[davidak@nixos:~/test]$ nix-shell 
these paths will be fetched (10.58 MiB download, 52.88 MiB unpacked):
  /nix/store/51zrpaysgqxr2m40h6qg4jhibzgpw09j-libxslt-1.1.32-py
  /nix/store/85nxa2jwgj3wqzyvc3wy8172fpml78qj-python-2.7.15
  /nix/store/8rf3qalbykr0y4l6wnmjgm9crgb82w52-python2.7-pip-9.0.1
  /nix/store/c8xna3dajanqz84jphwg08nca18cmfx0-libzip-1.3.0-dev
  /nix/store/ddcp1awgbcnkbg4crkqv6pqmawqa61vj-libzip-1.3.0
  /nix/store/gjqbxhyjsvn1j0z3m3ld7l5v6kczib2c-python-recursive-pth-loader-1.0
  /nix/store/m9d4pfi6kag8mc0i1zxl1zzsnwzc6x8y-python2.7-virtualenv-15.1.0
copying path '/nix/store/gjqbxhyjsvn1j0z3m3ld7l5v6kczib2c-python-recursive-pth-loader-1.0' from 'https://cache.nixos.org'...
copying path '/nix/store/51zrpaysgqxr2m40h6qg4jhibzgpw09j-libxslt-1.1.32-py' from 'https://cache.nixos.org'...
copying path '/nix/store/85nxa2jwgj3wqzyvc3wy8172fpml78qj-python-2.7.15' from 'https://cache.nixos.org'...
copying path '/nix/store/8rf3qalbykr0y4l6wnmjgm9crgb82w52-python2.7-pip-9.0.1' from 'https://cache.nixos.org'...
copying path '/nix/store/ddcp1awgbcnkbg4crkqv6pqmawqa61vj-libzip-1.3.0' from 'https://cache.nixos.org'...
copying path '/nix/store/m9d4pfi6kag8mc0i1zxl1zzsnwzc6x8y-python2.7-virtualenv-15.1.0' from 'https://cache.nixos.org'...
copying path '/nix/store/c8xna3dajanqz84jphwg08nca18cmfx0-libzip-1.3.0-dev' from 'https://cache.nixos.org'...
New python executable in /home/davidak/test/venv/bin/python2.7
Also creating executable in /home/davidak/test/venv/bin/python
Installing pip, wheel...done.
Traceback (most recent call last):
  File "/home/davidak/test/venv/bin/pip", line 7, in <module>
    from pip._internal import main
ImportError: No module named _internal

Same with Python 3:

...
Traceback (most recent call last):
  File "/home/davidak/code/mein/venv/bin/pip", line 7, in <module>
    from pip._internal import main
ImportError: No module named 'pip._internal'

related to #26876 #33713 #39558

cc @domenkozar

Steps to reproduce

1. copy example into default.nix as is https://nixos.org/nixpkgs/manual/#how-to-consume-python-modules-using-pip-in-a-virtualenv-like-i-am-used-to-on-other-operating-systems
2. create requirements.txt with "requests" as content
3. nix-shell

Technical details

• system: "x86_64-linux"
• host os: Linux 4.14.55, NixOS, 18.03.132865.411cc559c05 (Impala)
• multi-user?: no
• sandbox: yes
• version: nix-env (Nix) 2.0.4
• channels(root): "nixos-18.03, nixos-hardware, nixos-unstable-18.09pre143771.a8c71037e04"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs

[FRidh]

Was added in #21837 by @Azulinho who may help.

[Azulinho]

yeap, I had that problem a few weeks ago, think it was related to some pip update
this is what I have on my default.nixs for python

┌─[azul][w520][~/nix-shell-profiles]
└─▪ cat python.nix 
with import <nixpkgs> {};
with pkgs.python27Packages;

buildPythonPackage { 
  name = "impurePythonEnv";
  buildInputs = [
    taglib
    openssl
    git
    libxml2
    libxslt
    libzip
    python27Full
    python27Packages.virtualenv
    python27Packages.pip
    stdenv
    libffi
    zlib ];
  src = null;
  # When used as `nix-shell --pure`
  shellHook = ''
  unset http_proxy
  export GIT_SSL_CAINFO=/etc/ssl/certs/ca-bundle.crt
  virtualenv --no-wheel --no-setuptools venv 
  wget -c https://bootstrap.pypa.io/get-pip.py
  venv/bin/python get-pip.py
  venv/bin/pip install -r requirements.txt --no-use-wheel
  venv/bin/pip install jedi
  venv/bin/pip install ipython==5.2.0
  venv/bin/pip install pylint
  venv/bin/pip install flake8
  export PATH=$PWD/venv/bin:$PATH
  '';
}

[FRidh]

think it was related to some pip update

Correct, pip 10 moved some private modules which certain tools were using.

[stale]

Thank you for your contributions.

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