+ The :meth:`.CacheRegion.invalidate` method now supports an option
+ ``hard=True|False``. A "hard" invalidation, equivalent to the
+ existing functionality of :meth:`.CacheRegion.invalidate`, means
+ :meth:`.CacheRegion.get_or_create` will not return the "old" value at
+ all, forcing all getters to regenerate or wait for a regeneration.
+ "soft" invalidation means that getters can continue to return the
+ old value until a new one is generated.
New dogpile-specific exception classes have been added, so that