mitchellh/vagrant — pull request #1497 by jedvardsson (2013-03-25 23:42:50+00:00)
Title: Faking user agent 'curl' to make dropbox http downloads work.

Dropbox assumes Vagrant is a browser, thus serving vagrant a download page instead of the linked file itself. Setting vagrant users agent to e.g. curl/7.29.0 solves this.