If you're using Vagrant >= 1.9.6, you can safely ignore this notice. Otherwise, please read on for affected versions and a workaround.
Affected Vagrant versions and release dates:
>= 1.7.0 (12/9/2014),
< v1.9.6 (6/28/2017)
If you'd like to continue using the versions mentioned above, you'll need to set the VAGRANT_SERVER_URL environment variable in order for box downloads/updates to continue working:
# macOS and Linux
# Windows (CMD)
# Windows (Powershell)
Thanks! -Justin