Filename tokens failing

It seems that the tokens for the -o / --output are failing.

In the provided example:

ytdl -o "{author.name} - {title}" "http://www.youtube.com/watch?v=_HSylqgVYQI"

The output filename is saved as:

{author.name} - {title}.mp4

I know the earlier versions of the utility didn't have this issue, but I was looking at the code, and it looks like a fair little bit has changed since I first downloaded ytdl back in April of 2018.