Error when running pypi2nix command

[Fresheyeball]

Description

Not sure why this is happening yet. But the cli tool made making this issue very easy, which makes me think you might want to know about it.

INFO: pypi2nix v2.0.1 running ...
INFO: Downloading wheels and creating wheelhouse ...
INFO: Installing runtime requirements
ERROR: Could not find a version that satisfies the requirement opencv-python (from -r /tmp/tmpg_4riq5_/cc998a7d486d1ac774633ddee5779f29.txt (line 1)) (from versions: none)
ERROR: No matching distribution found for opencv-python (from -r /tmp/tmpg_4riq5_/cc998a7d486d1ac774633ddee5779f29.txt (line 1))

% pypi2nix --version
% pypi2nix -V python37 -e opencv-python

[seppeljordan]

Two things:

1. opencv-python does not have a source distribution. You have three options here:
   1. Open an issue with the opencv-python and ask the maintainers to upload a source distribution
   2. Find the latest version of opencv-python which HAS a source distribution and use that. Let's say the latest source distribution is 1.2.3 then you would invoke pypi2nix like that: pypi2nix -e opencv-python==1.2.3.
   3. You try building from source (github repo). Invokation would be: pypi2nix -e 'git+https://github.com/skvark/opencv-python#egg=opencv-python'
2. Building opencv yourself looks like going through a world of pain. Check out https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/opencv/4.x.nix Unfortunately pypi2nix will be of little assistance in the process. If you are successful though, let me know.

If you just want opencv-python to "just work" you could just use the version that is packaged with nixpkgs (which I recommend). But if you are eager to get this working with pypi2nix I could assist you. And if you have a lot of time on your hands we could collaborate to bring pypi2nix to a place where these thing are manageable for people other than hyper intelligent space wizards and witches.