The file format used by all p* command line scripts such as pserve and pshell , as well as the pyramid.paster.bootstrap() function is now replaceable thanks to a new dependency on plaster. For now, Pyramid is still shipping with integrated support for the PasteDeploy INI format by depending on the plaster_pastedeploy binding library. This may change in the future so it is recommended for applications to start depending on the appropriate plaster binding for their needs. See https://github.com/Pylons/pyramid/pull/2985

Added an execution policy hook to the request pipeline. An execution policy has the ability to control creation and execution of the request objects before they enter the rest of the pipeline. This means for a single request environ the policy may create more than one request object. The execution policy can be replaced using the new pyramid.config.Configurator.set_execution_policy() config directive. The first library to use this feature is pyramid_retry. Pyramid's default execution policy will attempt to handle and render uncaught exceptions. This is a subtle, but fundamental, change indicating that an exception view may expect to be called outside of the default EXCVIEW tween. There are various predicates available to assist in defining valid exception views for various parts of the pipeline. For example, pyramid_tm defines the tm_active=True predicate which can be applied to exception views that require access to the default transaction. In general this means that exception views may be expected to cover more possible error conditions, including when exceptions occur from tweens that are placed OVER the EXCVIEW tween. If necessary, when provided a response object, you may inspect request.exception or request.exc_info to determine if the response was generated as the result of an exception. See https://github.com/Pylons/pyramid/pull/2964