tarsnapper: use pynose to run tests

The nosetests support was removed from pytest in version 8, so revert to
using the nosetests entry point to run tests.

While I'm in here already, update to use pynose to avoid future failures
when nose is removed from nixpkgs (see #311054).

(cherry picked from commit f6660806b8)

pkgs/tools/backup/tarsnapper/default.nix

@@ -37,8 +37,7 @@ python3Packages.buildPythonApplication rec {
   ];
 
   nativeCheckInputs = with python3Packages; [
-    pytestCheckHook
-    nose
+    pynose
   ];
 
   # Remove standard module argparse from requirements
@@ -46,6 +45,12 @@ python3Packages.buildPythonApplication rec {
 
   makeWrapperArgs = [ "--prefix PATH : ${lib.makeBinPath [ tarsnap ]}" ];
 
+  checkPhase = ''
+    runHook preCheck
+    nosetests tests
+    runHook postCheck
+  '';
+
   pythonImportsCheck = [ "tarsnapper" ];
 
   meta = with lib; {