GrowthExperiments has a number of hacks and conveniences for running in a development or testing environment, to use services from a production wiki and then deal with the fact that the returned pages don't exist locally. This can result in bugs having unexpected side effects, such as T266600: Newcomer tasks: edit tag not applying to all edits. We should have a flag for differentiating between production and testing environments, and validate data more aggressively in production mode (with the assumption that the article associated with the task must exist).