Uploading a file by passing a file handler yields `repr(fh)` instead of its contents

I'm not very familiar with the `requests` (or `pyodide-http`) library, but could it happen that `.read()` method is not called?

I found this in https://requests.readthedocs.io/en/latest/_modules/requests/models/#PreparedRequest :
```
elif hasattr(fp, "read"):
    fdata = fp.read()
```

...or am I doing something wrong? 🤔 

I can add an example to reproduce later if needed!