Removed fatal errors from Py_Initmodule4() (and thus from Py_Initmodule(), which is a macro wrapper around it). The return value is now a NULL pointer if the initialization failed. This may make old modules fail with a SEGFAULT, since they don't expect this kind of failure. That's OK, since (a) it "never" happens, and (b) they would fail with a fatal error otherwise, anyway. Tons of extension modules should now check the return value of Py_Initmodule*() -- that's on my TODO list.