Uploading new patch with the following changes:

- Allow length 1 bytes object as argument to %c.
- Make %r an alias for %a.

I will upload a draft PEP (proposed as a replacement for 461).

Victor, thanks for the review.  My reply is:

- regarding duplicated code: almost all of the code I added came directly from Python 2.7.  If it can but shared with unicode object, great.  However, note that the Python 2.7 code is well tested and well optimized.

- regarding the introduction of __ascii__, see my draft PEP.  PEP 461 cannot be implemented, adding __bytes__ to number objects breaks backwards compatibility.

- regarding the change to _datetime, I don't mind if it gets discarded but I think its useful behavior.  Mostly I made it as a proof-of-concept.