anchor.diff:  
     src = fetchurl {
       url = tarballUrls version;
  -    sha256 = "af6ba39142220687c500f79b4aa2f181d9b24e4f8d8ec497cea4ba26c64bedaf";
  +    hashOutput = false;
  +    sha256 = "f98f2d97b11851cbe7c2d4b4eaef498ae9d17a3c2ef1401609b7b4ca66655b8a";
     };
   
     nativeBuildInputs = [
  
positive.code: }:
  
  let
    version = "1.15.1";
  
    tarballUrls = version: [
      "mirror://gnu/automake/automake-${version}.tar.xz"
  
negative.code: 
    passthru = {
      srcVerification = fetchurl rec {
        failEarly = true;
        urls = tarballUrls "1.16";
        pgpsigUrls = map (n: "${n}.sig") urls;
        pgpKeyFingerprints = [
          # Mathieu Lirzin
          "F2A3 8D7E EB2B 6640 5761  070D 0ADE E100 9460 4D37"
        ];
        outputHash = "f98f2d97b11851cbe7c2d4b4eaef498ae9d17a3c2ef1401609b7b4ca66655b8a";
        inherit (src) outputHashAlgo;
      };
    };
  
  