Our RESTful API won't be using the two modules included in the metrics/metrics/views subfolder that was generated by the app template. Thus, we must delete the metrics/metrics/views/default.py and metrics/metrics/views/notfound.py files.
Pyramid uses view callables as the main building blocks for a RESTful API. Whenever a request arrives, Pyramid finds and invokes the appropriate view callable to process the request and return an appropriate response.