Efficient and secure document rendering from multiple similar untrusted sources

Previously, only trusted maintainers could modify the content of Nauč se Python!, a project for educational content deployed to the web. The goal of this thesis was to allow for some of the content to be rendered from forks of the base Git repository, but safely and efficiently. That was accomplished by creating a tool which can run Python code in various levels of isolation and cache the results. This tool was then integrated into the Nauč se Python! project, building parts of the website in an isolated environment, either in Docker containers or in virtual machines managed by Vagrant, and sharing appropriate content fragments across repositories.