Recent research has shown the great potential of automatic feedback in education. This paper presents SOBO, a bot we designed to automatically provide feedback on code quality to undergraduate students. SOBO has been deployed in a course at the KTH Royal Institute of Technology in Sweden with 130+ students. Overall, SOBO has analyzed 1687 GitHub repositories and produced 8443 tailored code quality feedback messages to students. Unlike traditional tools embedded in CI pipelines, SOBO is designed to interact with students in a way that promotes personalized learning without imposing additional teaching burdens. The quantitative and qualitative results indicate that SOBO effectively nudges students into adopting code quality best practices, without interfering with pedagogical objectives. From this experience, we provide guidelines on how to design and deploy teaching bots in programming courses.