GitLab is used only for code review, issue tracking and project management. Canonical locations for source code are still https://gitweb.torproject.org/ https://git.torproject.org/ and git-rw.torproject.org.
Like other online users, Cloudflare's DNS sometimes return their own internal IP address. This behaviour results in DNS error screen.
You better ask Tor exit owners to change their DNS server to ISP one, or run unbound locally.