Apply two changes, systematically:

(1) Use PyErr_NewException("module.class", NULL, NULL) to create the
    exception object.

(2) Remove all calls to Py_FatalError(); instead, return or
    ignore the errors -- the import code now checks PyErr_Occurred()
    after calling a module's init function, so it's no longer a
    fatal error for the initialization to fail.

Also did some small cleanups, e.g. removed unnecessary test for
"already initialized" from initfpectl(), and unified
initposix()/initnt().

I haven't checked this very thoroughly, so while the changes are
pretty trivial -- beware of untested code!
diff --git a/Modules/zlibmodule.c b/Modules/zlibmodule.c
index bc1b6f8..98dbfa5 100644
--- a/Modules/zlibmodule.c
+++ b/Modules/zlibmodule.c
@@ -801,7 +801,7 @@
 			   zlib_module_documentation,
 			   (PyObject*)NULL,PYTHON_API_VERSION);
         d = PyModule_GetDict(m);
-        ZlibError = Py_BuildValue("s", "zlib.error");
+        ZlibError = PyErr_NewException("zlib.error", NULL, NULL);
         PyDict_SetItemString(d, "error", ZlibError);
 
 	insint(d, "MAX_WBITS", MAX_WBITS);
@@ -815,7 +815,4 @@
 	insint(d, "Z_DEFAULT_STRATEGY", Z_DEFAULT_STRATEGY);
 	ver = PyString_FromString(ZLIB_VERSION);
 	PyDict_SetItemString(d, "ZLIB_VERSION", ver);
-
-        if (PyErr_Occurred())
-                Py_FatalError("can't initialize module zlib");
 }