gdb pretty printers and python3.x

Starting with gdb-7.6, gdb supports embedding a Python3 interpreter instead of
Python2.  However most pretty printers are still using Python2 code, and when
shipping a gdb using Python3, you have to fix all pretty printers at once (and
keep building it with Python2, nobody will port to Python3).  So some questions:

 - Is there a list of known pretty printers?  So far I know about
   libstdc++, python, gtk, libreoffice.

 - Is there a minimal python version supported by gdb?  If e.g. it is 2.6,
   then probably most pretty printers could be converted to code which can
   be used by both 2.x and 3.x.  If not, then it would be up to 2to3 runs
   to do the conversion when needed.

 - Has somebody already done such a 3.x based build, and maybe already
   has converted some of the pretty printers?

Thanks, Matthias