title: How to use nix-shell to install playwright from PyPi?
body: <p>I am trying to create a <code>nix-shell</code> that installs <code>python</code> and <code>playwright</code>. My code does install python, but I cannot installed <code>playwright</code> properly.</p>
  <pre class="lang-hs prettyprint-override"><code>with (import &lt;nixpkgs&gt; {});
  
  let
    playwright = pkgs.python38Packages.buildPythonPackage rec {
      pname = &quot;playwright&quot;;
      version = &quot;1.12.1&quot;;
  
      src = pkgs.python38Packages.fetchPypi {
        inherit pname version;
      };
  
      propagatedBuildInputs = with pkgs.python38Packages; [];
  
      doCheck = false;
    };
  
    customPython = pkgs.python38.buildEnv.override {
      extraLibs = [ playwright ];
    };
  in
  
  pkgs.mkShell {
    buildInputs = [ customPython ];
  }
  </code></pre>
  <p>And this gives me the following error:</p>
  <pre><code>while evaluating the attribute 'outPath' at /nix/store/gjqpc2i5nbi1yrzm0caaryvs8y1nhc8h-nixpkgs-21.11pre292293.84aa23742f6/nixpkgs/lib/customisation.nix:164:7:
  while evaluating the attribute 'src' of the derivation 'python3.8-playwright-1.12.1' at /nix/store/gjqpc2i5nbi1yrzm0caaryvs8y1nhc8h-nixpkgs-21.11pre292293.84aa23742f6/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:201:11:
  hash '' has wrong length for hash type 'sha256'
  </code></pre>
  <p>How can I fix its hash?</p>