rewrite always finishes with an error when the file is on a Windows host

Trying to run iotedgedev in a docker container inside a WSL2 vm always yields the same error:

ERROR: Could not update the environment variable IOTHUB_CONNECTION_STRING in file /home/iotedge/.env

Funny thing is, the variable IS written to the file. What isn't written is the next variable, so clearly an error occurs AFTER having already written the value to the file.

Iotedgedev uses dotenv to update the .env file:

    def save_envvar(self, key, value):
        try:
            dotenv_file = self.get_dotenv_file()
            dotenv_path = os.path.join(os.getcwd(), dotenv_file)
            set_key(dotenv_path, key, value)
        except Exception:
            raise IOError(f("Could not update the environment variable {key} in file {dotenv_path}"))

Now, set_key seems to be using rewrite to update the file, and rewrite does this:

    if error is None:
        shutil.move(dest.name, path)
    else:
        os.unlink(dest.name)
        raise error from None

Instead of plain move it should first do an os.remove and only then move. That should make it work with files on a Windows host.

Start at save_envvar and trace set_key into the rewrite path shown in the report. Reproduce the .env update with a file on a Windows host or WSL2-mounted path, then verify that the update finishes without an error and that subsequent variables are written.