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/utils.py

@@ -0,0 +1,51 @@
+import json
+
+from ansible.compat.tests.mock import patch
+from ansible.module_utils import basic
+from ansible.module_utils.six.moves import xmlrpc_client
+from ansible.module_utils._text import to_bytes
+
+
+def set_module_args(args):
+    args = json.dumps({'ANSIBLE_MODULE_ARGS': args})
+    basic._ANSIBLE_ARGS = to_bytes(args)
+
+
+class AnsibleExitJson(Exception):
+    pass
+
+
+class AnsibleFailJson(Exception):
+    pass
+
+
+def exit_json(*args, **kwargs):
+    if 'changed' not in kwargs:
+        kwargs['changed'] = False
+    raise AnsibleExitJson(kwargs)
+
+
+def fail_json(*args, **kwargs):
+    kwargs['failed'] = True
+    raise AnsibleFailJson(kwargs)
+
+
+def get_method_name(request_body):
+    return xmlrpc_client.loads(request_body)[1]
+
+
+def mock_request(responses, module_name):
+    def transport_request(host, handler, request_body, verbose=0):
+        """Fake request"""
+        method_name = get_method_name(request_body)
+        excepted_name, response = responses.pop(0)
+        if method_name == excepted_name:
+            if isinstance(response, Exception):
+                raise response
+            else:
+                return response
+        else:
+            raise Exception('Expected call: %r, called with: %r' % (excepted_name, method_name))
+
+    target = '{0}.xmlrpc_client.Transport.request'.format(module_name)
+    return patch(target, side_effect=transport_request)