debugpy.listen() throws exception because sys.argv is missing

[abhijit-sawant]

Environment data

• debugpy version: 1.0.0b11
• OS and version: Windows 10
• Python version : 3.5 ActiveState
• Using VS Code or Visual Studio: VS Code

Actual behavior

I am using debugpy with embedded python interpreter. As its embedded interpreter I chose not to set argc and argv. But debugpy.listen() method expects sys.argv and throws exception as shown below -

File "<install_location>\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_comm.py", line 330, in _on_run
    self.process_net_command_json(self.py_db, json_contents)

File "<install_location>\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_process_net_command_json.py", line 190, in process_net_command_json
    cmd = on_request(py_db, request)

File "<install_location>\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_process_net_command_json.py", line 441, in on_attach_request
    return self._handle_launch_or_attach_request(py_db, request, start_reason='attach')

File "<install_location>\debugpy\debugpy-1.0.0b11\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_process_net_command_json.py", line 424, in _handle_launch_or_attach_request
    self._send_process_event(py_db, start_reason)

File "<install_location>\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_process_net_command_json.py", line 405, in _send_process_event
    if len(sys.argv) > 0:
AttributeError: module 'sys' has no attribute 'argv'

Expected behavior

I would expect debugpy to work even without sys.argv as it can be used with embedded interpreter and setting sys.argv is optional. But I am not certain its practical and how big that change is.

Steps to reproduce:

1. Write C++/C code that initializes python interpreter (Py_Intialize())
2. Run following code using python C API in embedded interpreter

    import debugpy
   debugpy.listen(5678)

3. Have following snippet in launch.json

        {
            "name": "Python: MyAttach",
            "type": "python",
            "request": "attach",
            "connect": {
                "host": "localhost",
                "port": 5678
            }
        }

4. Build code, launch and attach
5. Check VS Code debug console. You will see the traceback mentioned above