Use newer version of pyutil.

nix/overlays.nix

@@ -15,6 +15,9 @@ self: super: {
       # slightly newer version than appears in nixos 19.09 is helpful.
       future = python-super.callPackage ./future.nix { };
 
+      # Need version of pyutil that supports Python 3. The version in 19.09
+      # is too old.
+      pyutil = python-super.callPackage ./pyutil.nix { };
     };
   };
 }

nix/pyutil.nix

@@ -0,0 +1,48 @@
+{ stdenv
+, buildPythonPackage
+, fetchPypi
+, setuptoolsDarcs
+, setuptoolsTrial
+, simplejson
+, twisted
+, isPyPy
+}:
+
+buildPythonPackage rec {
+  pname = "pyutil";
+  version = "3.3.0";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "8c4d4bf668c559186389bb9bce99e4b1b871c09ba252a756ccaacd2b8f401848";
+  };
+
+  buildInputs = [ setuptoolsDarcs setuptoolsTrial ] ++ (if doCheck then [ simplejson ] else []);
+  propagatedBuildInputs = [ twisted ];
+
+  # Tests fail because they try to write new code into the twisted
+  # package, apparently some kind of plugin.
+  doCheck = false;
+
+  prePatch = stdenv.lib.optionalString isPyPy ''
+    grep -rl 'utf-8-with-signature-unix' ./ | xargs sed -i -e "s|utf-8-with-signature-unix|utf-8|g"
+  '';
+
+  meta = with stdenv.lib; {
+    description = "Pyutil, a collection of mature utilities for Python programmers";
+
+    longDescription = ''
+      These are a few data structures, classes and functions which
+      we've needed over many years of Python programming and which
+      seem to be of general use to other Python programmers. Many of
+      the modules that have existed in pyutil over the years have
+      subsequently been obsoleted by new features added to the
+      Python language or its standard library, thus showing that
+      we're not alone in wanting tools like these.
+    '';
+
+    homepage = "http://allmydata.org/trac/pyutil";
+    license = licenses.gpl2Plus;
+  };
+
+}