fixed object.__new__ error message for >=2.7.4

Looks like this error message changed in 2.7.4... I don't know how you want to handle this kind of thing in general but this would make it a lot more convenient for me to run all the tests.
Let's define this the same way as CPython's PY_VERSION_HEX -- they leave an additional 8 bits for information such as "release level" (alpha/beta/rc/final) and "serial" (rc1, rc2), see include/patchlevel.h