In commit 5a4921a1a we replaced `URI.parse` with `URI.open` due to some
issues during our tests with S3.
However, there are some security issues with `URI.open` [1], since it
might allow some users to execute code on the server.
So we're using `URI.parse#open` instead.
[1] https://docs.rubocop.org/rubocop/cops_security.html#securityopen