Obnam 3: Logging

Goal Today I want to address some long-standing, but fairly minor issues in the Obnam project. Plan Add some logging and remove debug prints. This requires picking a logging system. That's a decision that can be changed later, so I'm going pick log and env_logger . It's possible we'll want tracing later, for structured logs if nothing else, but I want to start small. The obnam.org web site needs…