udocker: fix build failure

use_2to3 was removed from setuptools with version 58.0.0. There is an
upstream issue for this error
(https://github.com/indigo-dc/udocker/issues/358) and has been resolved
with commit
9f7d6c5f9a.
We apply this commit as a patch.

Disable test_02__load_structure because it fails with a
unittest.mock.InvalidSpecError.

pkgs/tools/virtualization/udocker/default.nix

@@ -2,6 +2,7 @@
 , fetchFromGitHub
 , singularity
 , python3Packages
+, fetchpatch
 }:
 
 python3Packages.buildPythonApplication rec {
@@ -24,11 +25,19 @@ python3Packages.buildPythonApplication rec {
     pycurl
   ]);
 
+  patches = [
+    (fetchpatch {
+      url = "https://github.com/indigo-dc/udocker/commit/9f7d6c5f9a3925bf87d000603c5b306d73bb0fa3.patch";
+      sha256 = "sha256-fiqvVqfdVIlILbSs6oDWmbWU9piZEI2oiAKUcmecx9Q=";
+    })
+  ];
+
   checkInputs = with python3Packages; [
     pytestCheckHook
   ];
 
   disabledTests = [
+    "test_02__load_structure"
     "test_05__get_volume_bindings"
   ];