Gmail API send message with attachments example not working

[lecovi]

Summary

https://github.com/googleworkspace/python-samples/blob/master/gmail/snippet/send%20mail/send_message_with_attachment.py it seems to be outdated.

Expected Behavior

Executing https://github.com/googleworkspace/python-samples/blob/master/gmail/snippet/send%20mail/send_message_with_attachment.py with proper credentials and a valid email address should send an email.

Actual Behavior

---------------------------------------------------------------------------
HttpError                                 Traceback (most recent call last)
Input In [203], in <cell line: 2>()
      1 # pylint: disable=E1101
      2 send_message = gmail_service.users().messages().send(
      3     userId="me",
      4     body=create_message
----> 5 ).execute()

File ~/src/ifts18/gworkspace-ifts18-helper/venv/lib/python3.10/site-packages/googleapiclient/_helpers.py:130, in positional.<locals>.positional_decorator.<locals>.positional_wrapper(*args, **kwargs)
    128     elif positional_parameters_enforcement == POSITIONAL_WARNING:
    129         logger.warning(message)
--> 130 return wrapped(*args, **kwargs)

File ~/src/ifts18/gworkspace-ifts18-helper/venv/lib/python3.10/site-packages/googleapiclient/http.py:938, in HttpRequest.execute(self, http, num_retries)
    936     callback(resp)
    937 if resp.status >= 300:
--> 938     raise HttpError(resp, content, uri=self.uri)
    939 return self.postproc(resp, content)

HttpError: <HttpError 400 when requesting https://gmail.googleapis.com/gmail/v1/users/me/messages/send?alt=json returned "'raw' RFC822 payload message string or uploading message via /upload/* URL required". Details: "[{'message': "'raw' RFC822 payload message string or uploading message via /upload/* URL required", 'domain': 'global', 'reason': 'invalidArgument'}]">

Steps to Reproduce the Problem

2. Copy code and paste it in your local computer
3. Execute with proper credentials
4. See the outcome

Specifications

• Python version (python --version): 3.10.4
• OS (Mac/Linux/Windows): Mac