In D4654#71289, @yuja wrote:

-class RevlogError(Hint, Exception):
+class StorageError(Hint, Exception):
+ """Raised when an error occurs in a storage layer.
+
+ Usually subclassed by a storage-specific exception.
+ """
+ bytes = _tobytes
+
+class RevlogError(StorageError):

__bytes__ = _tobytes

Perhaps LookupError will have to be either reparented to StorageError
or detached from the storage-type error. Just a note. I think you would have
some plan.

In D4642#71269, @yuja wrote:

+ Extensions should wrap these factory functions to customize repository type
+ creation. Note that an extension's wrapped function may be called even if
+ that extension is not loaded for the repo being constructed. Extensions
+ should check if their `__name__` appears in the
+ `extensionmodulenames` set passed to the factory function and no-op if
+ not.

I assume this will be revisited later. I think it's a source of bugs to
relying on extensions to check if they are enabled. It's also cumbersome
to wrap a function referenced from another table.