pip module: fix TypeError (#31395)

* pip: add test: an error occurs when pip not found
* pip: fix TypeError exception when pip executable isn't found

test/units/modules/packaging/language/test_pip.py

@@ -0,0 +1,26 @@
+import json
+
+from ansible.compat.tests import unittest
+from ansible.compat.tests.mock import patch
+from ansible.module_utils import basic
+
+from ansible.modules.packaging.language import pip
+
+from ..utils import (set_module_args, AnsibleFailJson, exit_json, fail_json)
+
+
+class TestPip(unittest.TestCase):
+
+    def setUp(self):
+        self.mock_ansible_module = patch.multiple(basic.AnsibleModule, exit_json=exit_json, fail_json=fail_json)
+        self.mock_ansible_module.start()
+        self.addCleanup(self.mock_ansible_module.stop)
+
+    @patch.object(basic.AnsibleModule, 'get_bin_path')
+    def test_failure_when_pip_absent(self, mock_get_bin_path):
+
+        mock_get_bin_path.return_value = None
+
+        with self.assertRaises(AnsibleFailJson):
+            set_module_args({'name': 'six'})
+            pip.main()