python3.7 venv fails to create a venv

[Valodim]

Describe the bug

python3.7.5 venv fails to create a venv for me.

To Reproduce

$ python3 -m venv .
Error: Command '['/tmp/tmp.mLxXFJyvRk/bin/python3.7', '-Im', 'ensurepip', '--upgrade', '--default-pip']' returned non-zero exit status 1.
$ ls
bin  include  lib  lib64  pyvenv.cfg
$ bin/python3.7 -Im ensurepip --upgrade --default-pip
Looking in links: /tmp/tmp4_tf3pzn
Collecting setuptools
Collecting pip
Installing collected packages: setuptools, pip
ERROR: Could not install packages due to an EnvironmentError: [Errno 30] Read-only file system: '/nix/store/k5rdcbcwwpvj7l9f1yvd5mfggcfz16kk-python3-3.7.5/lib/python3.7/site-packages/easy_install.py'

Expected behavior

A working venv :)

virtualenv does work as expected

Metadata

• system: "x86_64-linux"
• host os: Linux 5.4.8, NixOS, 19.09.1806.b047b7315d8 (Loris)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3.2
• channels(valodim): "home-manager-19.09, nixpkgs-19.09.1850.5dc4d071ffe"
• channels(root): "nixos-19.09.1850.5dc4d071ffe"
• nixpkgs: /home/valodim/.nix-defexpr/channels/nixpkgs

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute: python37
# a list of nixos modules affected by the problem
module:

[jonringer]

pip is special in venv, most other packages should work fine, also, the workflow is:

$ nix-shell -p python3Packages.virtualenv
$ virtualenv venv
...
$ source ./venv/bin/activate

[jonringer]

related: #77569

[Valodim]

so it's expected behavior that python -m venv . fails? the documentation created in #77569 reads like exactly that call should still work, and it desn't look like anything special is added to the environment for that.

[jonringer]

at least on unstable, this works for me

[07:38:49] jon@jon-desktop /home/jon/projects/nixpkgs (master)
$ nix-shell -p python3Packages.virtualenv

[nix-shell:/home/jon/projects/nixpkgs]$ python -m venv venv

[nix-shell:/home/jon/projects/nixpkgs]$ ls
COPYING  default.nix  doc  lib  maintainers  nixos  pkgs  README.md  venv

[nix-shell:/home/jon/projects/nixpkgs]$ source venv/bin/activate
bash: hash: hashing disabled
bash: hash: hashing disabled
(venv)
[nix-shell:/home/jon/projects/nixpkgs]$ pip install requests
Collecting requests
  Using cached https://files.pythonhosted.org/packages/51/bd/23c926cd341ea6b7dd0b2a00aba99ae0f828be89d72b2190f27c11d4b7fb/requests-2.22.0-py2.py3-none-any.whl
Collecting chardet<3.1.0,>=3.0.2 (from requests)
  Using cached https://files.pythonhosted.org/packages/bc/a9/01ffebfb562e4274b6487b4bb1ddec7ca55ec7510b22e4c51f14098443b8/chardet-3.0.4-py2.py3-none-any.whl
Collecting urllib3!=1.25.0,!=1.25.1,<1.26,>=1.21.1 (from requests)
  Downloading https://files.pythonhosted.org/packages/b4/40/a9837291310ee1ccc242ceb6ebfd9eb21539649f193a7c8c86ba15b98539/urllib3-1.25.7-py2.py3-none-any.whl (125kB)
     |████████████████████████████████| 133kB 11.2MB/s
Collecting certifi>=2017.4.17 (from requests)
  Downloading https://files.pythonhosted.org/packages/b9/63/df50cac98ea0d5b006c55a399c3bf1db9da7b5a24de7890bc9cfd5dd9e99/certifi-2019.11.28-py2.py3-none-any.whl (156kB)
     |████████████████████████████████| 163kB 15.3MB/s
Collecting idna<2.9,>=2.5 (from requests)
  Using cached https://files.pythonhosted.org/packages/14/2c/cd551d81dbe15200be1cf41cd03869a46fe7226e7450af7a6545bfc474c9/idna-2.8-py2.py3-none-any.whl
Installing collected packages: chardet, urllib3, certifi, idna, requests
Successfully installed certifi-2019.11.28 chardet-3.0.4 idna-2.8 requests-2.22.0 urllib3-1.25.7
WARNING: You are using pip version 19.2.3, however version 19.3.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
(venv)
[nix-shell:/home/jon/projects/nixpkgs]$

[jonringer]

just confirmed it works on release-19.09

please do

nix-channels --update
sudo !!

to update your nixpkgs and nixos channels

[jonringer]

the other thing that could be happening is that a pip package from the outer scope exists, in which case you could just do:

nix-shell --pure -p python3Packages.virtualenv

and it will remove everything but what you specified, however, this will remove anything else you had in your previous env

[Valodim]

Yup, works again. Very odd. I had done nix-channel --update very recently. Guess it vanished with an update. Thanks for looking into it :)

[GuillaumeDesforges]

Issue sometimes happen again. Using virtualenv .venv instead of python -m venv .venv is indeed a workaround.