Migrate a vBulletin 4 forum to Discourse

I was following your guide to import my vBulletin forum to Discourse. I am using a docker container for Discourse. I ran the following command:

I got a long list of errors:

sudo: no tty present and no askpass program specified
sudo: no tty present and no askpass program specified
[...]
sudo: no tty present and no askpass program specified
sudo: no tty present and no askpass program specified

Bundler::SudoNotPermittedError: Bundler requires sudo access to install at the moment. Try installing again, granting Bundler sudo access when
prompted, or installing into a different path.
An error occurred while installing rake (11.2.2), and Bundler cannot continue.
Make sure that `gem install rake -v '11.2.2'` succeeds before bundling.

I am new to ruby on rails and dockers. I do understand the concept of gems and Bundler.
What do these errors mean and how can I resolve them?