Bump flake's Nix version and fix some build errors

- discuss: `yacc` got renamed to / merged into `bison` apparently
- python-afs:
  - upstream actually has a Python 3 port, so just use that
  - `nose` is apparently old and deprecated; it looks like this build
    doesn't run the python-afs tests anyway, so no further changes are
    needed

Author: dehnert

flake.lock

@@ -30,7 +30,7 @@ in stdenv.mkDerivation {
     autoreconfHook
     libkrb5
     pkgs.e2fsprogs  # ss_perror
-    pkgs.yacc
+    pkgs.bison
     pkgs.nettools
     pkg-config	# needed by debathena-aclocal
     debathena-aclocal

pkgs/discuss.nix

@@ -8,10 +8,10 @@ in buildPythonPackage {
   version = "0.2.2";
 
   src = fetchFromGitHub {
-    owner = "dehnert";
+    owner = "macathena";
     repo = "python-afs";
-    rev = "2a12421d4b94fbfecf6ea3cec459848a651f6be1"; # nix branch
-    hash = "sha256-5tiABlKD3Vbb+fSrxVcZmqqi0ArBEwbJDhslk/r/QGs=";
+    rev = "300a92404859ed99a8d9db066b9526c363760e21"; # py3 branch
+    hash = "sha256-pm3UCNqUKSzlfOk4jTenrg6PH8SMRgrRQE4uABXvXD0=";
   };
 
   build-system = [
@@ -25,7 +25,6 @@ in buildPythonPackage {
 
   nativeBuildInputs = [
     python3.pkgs.cython
-    python3.pkgs.nose
   ];
 
   pythonImportsCheck = [