https://bugs.winehq.org/show_bug.cgi?id=45713
--- Comment #10 from Stellarspace macariopatrick@icloud.com --- (In reply to Fabian Maurer from comment #7)
How do you know it was trying to download that file?
I found a post on the forums that indicates that a user on native Windows was getting the same error message. They uninstalled Unity Web Player and installed it again. Maybe a reinstall isn't good enough. It's too bad the launcher automatically installs Unity Web Player. I don't think I can prevent that from happening without developer assistance.