_netrc file is not found under Windows, use .netrc instead (until Python's netrc library fixes how it handles this)

[Simon-Stone]

While it is correct that the netrc file is commonly called _netrc on Windows, the Python library netrc that is used here to read the file looks for .netrc on Windows by default. This appears to be something that may change soon, but for now using _netrc on Windows leads to an error, while .netrc works just fine.