udocker: Fix build (#57002)

The latest changes to support better cross-compilation compatibility
have introduced a stricter handling of dependency specifications in
python. Since b4acd97, mock and nosetest should be checkInputs, since
they are used for testing.

Fixes: #56972

pkgs/tools/virtualization/udocker/default.nix

@@ -12,7 +12,7 @@ buildPythonApplication rec {
     sha256 = "134xk7rfj0xki9znryk5qf1nsfa318ahrrsi1k6ia7kipp7i3hb4";
   };
 
-  buildInputs = [ proot patchelf fakechroot runc simplejson pycurl coreutils nose mock ];
+  buildInputs = [ proot patchelf fakechroot runc simplejson pycurl coreutils ];
 
   postPatch = ''
       substituteInPlace udocker.py --replace /usr/sbin:/sbin:/usr/bin:/bin $PATH
@@ -22,6 +22,11 @@ buildPythonApplication rec {
       substituteInPlace udocker.py --replace "autoinstall = True" "autoinstall = False"
   '';
 
+  checkInputs = [
+    nose
+    mock
+  ];
+
   checkPhase = ''
     NOSE_EXCLUDE=test_03_create_repo,test_04_is_repo,test_02__get_group_from_host nosetests -v tests/unit_tests.py
   '';