Package an upgraded Nevow, required because of the newer Twisted

nix/default.nix

@@ -1,4 +1,2 @@
-{ pkgs ? import <nixpkgs> { } }:
-pkgs.python2.pkgs.callPackage ./tahoe-lafs.nix {
-  eliot = (pkgs.python2.pkgs.callPackage ./eliot.nix { });
-}
+{ pkgs ? import <nixpkgs> { overlays = [ (import ./overlays.nix) ]; } }:
+pkgs.python2.pkgs.callPackage ./tahoe-lafs.nix { }

nix/nevow.nix

@@ -0,0 +1,46 @@
+{ stdenv, buildPythonPackage, fetchFromGitHub, isPy3k, twisted }:
+
+buildPythonPackage rec {
+  pname = "Nevow";
+  version = "0.15.0";
+  name = "${pname}-${version}";
+  disabled = isPy3k;
+
+  src = fetchFromGitHub {
+    owner = "twisted";
+    repo = "nevow";
+    rev = "aff713a6884a0ebf2214af5cfa3c1ea2d7d70669";
+    sha256 = "0wmfin9igj46dazyfkphk7jxqalvxisn2hjz79maqg4nbl0x3rcv";
+  };
+
+  propagatedBuildInputs = [ twisted ];
+
+  checkInputs = [ twisted ];
+
+  checkPhase = ''
+    trial formless nevow
+  '';
+
+  meta = with stdenv.lib; {
+    description = "Nevow, a web application construction kit for Python";
+    longDescription = ''
+      Nevow - Pronounced as the French "nouveau", or "noo-voh", Nevow
+      is a web application construction kit written in Python.  It is
+      designed to allow the programmer to express as much of the view
+      logic as desired in Python, and includes a pure Python XML
+      expression syntax named stan to facilitate this.  However it
+      also provides rich support for designer-edited templates, using
+      a very small XML attribute language to provide bi-directional
+      template manipulation capability.
+
+      Nevow also includes formless, a declarative syntax for
+      specifying the types of method parameters and exposing these
+      methods to the web.  Forms can be rendered automatically, and
+      form posts will be validated and input coerced, rendering error
+      pages if appropriate.  Once a form post has validated
+      successfully, the method will be called with the coerced values.
+    '';
+    homepage = https://github.com/twisted/nevow;
+    license = licenses.mit;
+  };
+}

nix/overlays.nix

@@ -0,0 +1,8 @@
+self: super: {
+  python27 = super.python27.override {
+    packageOverrides = python-self: python-super: {
+      eliot = python-self.callPackage ./eliot.nix { };
+      nevow = python-super.nevow.overrideAttrs (old: { doCheck = false; }); # callPackage ./nevow.nix { };
+    };
+  };
+}