Hmm. Curl also succeeds for me but I get the following when I
vagrant up
==> default: Adding box 'discourse-16.04' (v0) for provider: virtualbox
default: Downloading: https://www.dropbox.com/s/2132770g1e05c6d/discourse.box?dl=1
An error occurred while downloading the remote file. The error
message, if any, is reproduced below. Please fix this error and try
again.
I must have misinterpreted the error.