Update zkapauthorize to use mach-nix and nixos-21.05.

nixos/pkgs/privatestorage.nix

 { pkgs, fetchFromGitHub, callPackage }:
 let
-  pypi-deps-db = fetchFromGitHub {
-    owner = "DavHau";
-    repo =  "pypi-deps-db";
-    rev = "dff83027fa68b7f70142a551efa4ebe1f018290a";
-    sha256 = "1plc6hgcraza9wwsziill7ig9hswpg8vzgm0yzwillc4vqrb5prr";
-  };
-  mach-nix = import (fetchFromGitHub {
-    owner = "DavHau";
-    repo = "mach-nix";
-    rev = "773580c35bcdb8cbd0820018d304686282f88d16";
-    sha256 = "105d6b6kgvn8kll639vx5adh5hp4gjcl4bs9rjzzyqz7367wbxj6";
-  })/* /tmp/mach-nix */ { inherit pkgs; pypiData = pypi-deps-db; python = "python27"; };
   zkap-authorizer-src = fetchFromGitHub {
-    owner = "PrivateStorageio";
+    owner = "tp-la";
     repo = "ZKAPAuthorizer";
-    rev = "e4430a0050cef286b723da7f8013c7affd5a58f7";
-    sha256 = "148d79zppsd6bnyagbx126s9x9yy975dx6rrbm26dh98kl1r8mbh";
-  };
-  zkap-authorizer = mach-nix.buildPythonPackage rec {
-    name = "ZKAPAuthorizer";
-    src = zkap-authorizer-src;
-    requirements = builtins.readFile ../../reqs;
-    providers = {
-      _default="wheel,sdist,nixpkgs"; #FIXME
-      autobahn = "wheel";
-      python-challenge-bypass-ristretto = "wheel"; #FIXME
-      boltons = "wheel";
-      humanize = "wheel";
-      tqdm = "wheel";
-      chardet = "wheel";
-      urllib3 = "wheel";
-      setuptools = "sdist";
-      pip = "sdist";
-      importlib-resources = "wheel";
-      tahoe-lafs = "sdist";
-    };
-    _.tahoe-lafs.patches = [ (
-      pkgs.fetchpatch {
-        url = "https://raw.githubusercontent.com/PrivateStorageio/nixpkgs/privatestorageio/pkgs/development/python-modules/tahoe-lafs/rsa-exponent.patch";
-        sha256 = "sha256-0vIMj5gZPbKLkow6wpA+Tz7bpyy+mZRSSFGmpg0VMyk=";
-      }
-      ) ]; 
-    meta.providers = providers;
-    meta._ = _;
+    # tomprince -- mach-nix branch
+    rev = "ca1e00a2ce8994bc088f06c81d8d68efb5678e43";
+    sha256 = "sha256-IJyuUpuy8hwqTkWRNhNwW7/v4/GmOKsbb9ickA2bTRc=";
   };
+  zkap-authorizer = callPackage (zkap-authorizer-src + "/new.nix") {};
 in 
-  mach-nix.mkPython {
-    inherit (zkap-authorizer.meta) providers _;
-    #requirements =  builtins.readFile ../../reqs;
-    packagesExtra = [ zkap-authorizer ];
-  }
+  pkgs.python27.withPackages (_: [zkap-authorizer])