gem: fix soundness issue when uninstalling default gems on Ubuntu (#10689)

* Attempt to fix gem soundness issue

* Return command execution

* Fix value error

* Attempt to fix failling tests

* Fix minor issues

* Update changelog

* Update tests/integration/targets/gem/tasks/main.yml

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

* Update changelogs/fragments/10689-gem-prevent-soundness-issue.yml

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

* Remove state and name from gem error message

* Improve gem uninstall check

* Make unit tests pass

* Fix linting issues

* gem: Remove length chenck and adapt unit tests

* Adapt gem unit tests

* gem: improve error msg

* Fix sanity error

* Fix linting issue

---------

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

tests/integration/targets/gem/tasks/main.yml

@@ -212,3 +212,18 @@
         that:
           - install_gem_result is changed
           - not gem_bindir_stat.stat.exists
+
+    - name: Attempt to uninstall default gem 'json'
+      community.general.gem:
+        name: json
+        state: absent
+      when: ansible_distribution == "Ubuntu"
+      register: gem_result
+      ignore_errors: true
+
+    - name: Assert gem uninstall failed as expected
+      when: ansible_distribution == "Ubuntu"
+      assert:
+        that:
+          - gem_result is failed
+          - gem_result.msg.startswith("Failed to uninstall gem 'json'")

tests/unit/plugins/modules/test_gem.py

@@ -52,7 +52,9 @@ class TestGem(ModuleTestCase):
 
     def patch_run_command(self):
         target = 'ansible.module_utils.basic.AnsibleModule.run_command'
-        return self.mocker.patch(target)
+        mock = self.mocker.patch(target)
+        mock.return_value = (0, '', '')
+        return mock
 
     def test_fails_when_user_install_and_install_dir_are_combined(self):
         with set_module_args({
@@ -107,12 +109,11 @@ class TestGem(ModuleTestCase):
 
             run_command = self.patch_run_command()
 
-            with pytest.raises(AnsibleExitJson) as exc:
+            with pytest.raises(AnsibleFailJson) as exc:
                 gem.main()
 
         result = exc.value.args[0]
-
-        assert result['changed']
+        assert result['failed']
         assert run_command.called
 
         assert '--install-dir /opt/dummy' in get_command(run_command)