self: super:
let

  # Pending upstream inclusion in https://github.com/NixOS/nixpkgs/pull/93377
  fallback-backoff = self.python3Packages.callPackage ({ lib, buildPythonPackage
    , fetchFromGitHub, pytestCheckHook, poetry, pytest-asyncio, }:
    buildPythonPackage rec {
      pname = "backoff";
      version = "1.10.0";
      src = fetchFromGitHub {
        owner = "litl";
        repo = pname;
        rev = "v${version}";
        sha256 = "1jj0l6pjx747d2yyvnzd3qbm4qr73sq6cc56dhvd8wqfbp5279x0";
      };
      format = "pyproject";
      nativeBuildInputs = [ poetry ];
      checkInputs = [ pytestCheckHook pytest-asyncio ];
    }) { };

  fallback-git-cache = self.python3Packages.callPackage
    ({ buildPythonPackage, fetchgit, git, backoff, mypy, }:
      buildPythonPackage rec {
        pname = "git-cache";
        version = "1.3.0";
        src = fetchgit {
          url = "https://scottworley.com/git-cache.git";
          rev = "v${version}";
          sha256 = "sha256-0HbtnS98im0sd2JIdUePBcspUskL2DY8ylQdyEC2sS0=";
        };
        propagatedBuildInputs = [ backoff ];
        checkInputs = [ git mypy ];
        doCheck = true;
        checkPhase = "./test.sh";
      }) { backoff = self.python3Packages.backoff or fallback-backoff; };

  fallback-pinch = self.python3Packages.callPackage
    ({ buildPythonPackage, fetchgit, nix, git, mypy, git-cache, }:
      buildPythonPackage rec {
        pname = "pinch";
        version = "3.0.3";
        src = fetchgit {
          url = "https://scottworley.com/pinch.git";
          rev = "v${version}";
          sha256 = "1j1y4h6m7fdb839h6igimqqjrdhr28wbzwa4b3grxp6szdpzkkra";
        };
        propagatedBuildInputs = [ git-cache ];
        checkInputs = [ nix git mypy ];
        doCheck = true;
        checkPhase = "./test.sh";
      }) { git-cache = self.python3Packages.git-cache or fallback-git-cache; };

in { pinch = super.pinch or fallback-pinch; }