One of the imports works for Newton but not Mitaka, leaving Mitaka
to fall back to a bunch of imports that don't work for it. Break
conditionals up.
Change-Id: If8d2ba23728646786ab29752b4207de9eece4d2d
Move all the backward compatibility conditions into
backward_compatibility.py for sanity. This includes a number
of module name-change management bits, and some monkey patching,
all of which existed in the codebase before; we're just trying
to rationalise the locations and the conditionals.
Change-Id: Ifa7769758c2f66f094da40fef67f5213094c43cd