$ vagrant up test
Bringing machine 'test' up with 'virtualbox' provider...
==> test: Box 'singularity-develop-0.20.1' could not be found. Attempting to find and install...
    test: Box Provider: virtualbox
    test: Box Version: >= 0
==> test: Adding box 'singularity-develop-0.20.1' (v0) for provider: virtualbox
    test: Downloading: https://vagrantcloud.com/tpetr/boxes/singularity-develop-0.20.1/versions/1/providers/virtualbox.box
An error occurred while downloading the remote file. The error
message, if any, is reproduced below. Please fix this error and try
again.

The requested URL returned error: 404 Not Found