re-use upstream tahoe-lafs nix packaging instead of duplicating it

default.nix

-{ pkgs ? import ./nixpkgs.nix { }, hypothesisProfile ? null, collectCoverage ? false, testSuite ? null, trialArgs ? null }:
-pkgs.python27Packages.zkapauthorizer.override { inherit hypothesisProfile collectCoverage testSuite trialArgs; }
+{ pkgs ? import <nixpkgs> { }
+, hypothesisProfile ? null
+, collectCoverage ? false
+, testSuite ? null
+, trialArgs ? null
+}:
+let pkgs' = pkgs.extend (import ./overlays.nix);
+in pkgs'.python27Packages.zkapauthorizer.override {
+  inherit hypothesisProfile collectCoverage testSuite trialArgs;
+}

overlays.nix

@@ -20,7 +20,7 @@ self: super: {
 
       # tahoe-lafs in nixpkgs is packaged as an application!  so we have to
       # re-package it ourselves as a library.
-      tahoe-lafs = python-self.callPackage ./tahoe-lafs.nix { };
+      tahoe-lafs = python-self.callPackage ((import ./tahoe-lafs.nix) + "/nix") { };
 
       # we depend on the privacypass python library, a set of bindings to the
       # challenge-bypass-ristretto Rust library

tahoe-lafs.nix

-{ fetchFromGitHub, nettools, python
-, twisted, foolscap, nevow, zfec
-, setuptools, setuptoolsTrial, pyasn1, zope_interface
-, service-identity, pyyaml, magic-wormhole, treq, appdirs
-, beautifulsoup4, eliot, autobahn, cryptography
-}:
-python.pkgs.buildPythonPackage rec {
-  version = "1.14.0.dev";
-  name = "tahoe-lafs-${version}";
-  src = fetchFromGitHub {
-    owner = "LeastAuthority";
+let
+  pkgs = import <nixpkgs> {};
+in
+  pkgs.fetchFromGitHub {
+    owner = "tahoe-lafs";
     repo = "tahoe-lafs";
-    # A branch of master with the storage plugin web resource reuse issue
-    # resolved.  https://tahoe-lafs.org/trac/tahoe-lafs/ticket/3265
-    rev = "1fef61981940bbd63ffc4242c3b589258622d117";
-    sha256 = "0kgkg7wd0nkj8f5p46341vjkr6nz3kf0fimd44d9kypm4rn8xczv";
-  };
-
-  postPatch = ''
-    sed -i "src/allmydata/util/iputil.py" \
-        -es"|_linux_path = '/sbin/ifconfig'|_linux_path = '${nettools}/bin/ifconfig'|g"
-
-    # Chroots don't have /etc/hosts and /etc/resolv.conf, so work around
-    # that.
-    for i in $(find src/allmydata/test -type f)
-    do
-      sed -i "$i" -e"s/localhost/127.0.0.1/g"
-    done
-  '';
-
-
-  propagatedBuildInputs = with python.pkgs; [
-    twisted foolscap nevow zfec appdirs
-    setuptoolsTrial pyasn1 zope_interface
-    service-identity pyyaml magic-wormhole treq
-    beautifulsoup4 eliot autobahn cryptography setuptools
-  ];
-
-  checkInputs = with python.pkgs; [
-    hypothesis
-    testtools
-    fixtures
-  ];
-
-  checkPhase = ''
-    $out/bin/tahoe --version
-  '';
-}
+    rev = "34aeefd3ddbf28dafbc3477e52461eafa53b545d";
+    sha256 = "0l8n4njbzgiwmn3qsmvzyzqlb0y9bj9g2jvpdynvsn1ggxrqmvsq";
+  }
\ No newline at end of file