[therein]

Thank you. I was able to move forward similarly as well. Good to see the solution I arrived at isn't too far from yours.

  self: super:
  {
    electrum = super.electrum.overrideAttrs(old: rec {
      preBuild = old.preBuild + ''
        # Patch unnecessarily tight dependency on ecdsa version
        substituteInPlace ./contrib/requirements/requirements.txt --replace 'ecdsa>=0.14' 'ecdsa>=0.13'
  
      additionalInputs = with super.python37Packages; [
        python-jsonrpc-server
      ];
  
      propagatedBuildInputs = old.propagatedBuildInputs ++ additionalInputs;
  
      src = super.fetchFromGitHub {
        owner = "spesmilo";
        repo = "electrum";
        rev = "223b62554ead397bb94013c0d9c95b63a0708ea6";
        sha256 = "05djndhdggsw0r9pqn3gnb31nvzghgcsg05r3f7b6hwz84zbl22r";
        fetchSubmodules = true;
      };
    });
  }

[iso-8859-1]

how do you know the dependency bound is too tight?

[takeda]

yes, it's possible that there was reason for requiring newer version, especially since it is a bitcoin wallet and this looks like a cryptographic library.

The better way would be to also update that package to required version.