save_global(): Trying to resolve module.name can fail for two

reasons:  importing module can fail, or the attribute lookup
module.name can fail.  We were giving the same error msg for
both cases, making it needlessly hard to guess what went wrong.
These cases give different error msgs now.

Modules/cPickle.c

@@ -2021,14 +2021,16 @@ save_global(Picklerobject *self, PyObject *args, PyObject *name)
 	mod = PyImport_ImportModule(module_str);
 	if (mod == NULL) {
 		cPickle_ErrFormat(PicklingError,
-				  "Can't pickle %s: it's not found as %s.%s",
-				  "OSS", args, module, global_name);
+				  "Can't pickle %s: import of module %s "
+				  "failed",
+				  "OS", args, module);
 		goto finally;
 	}
 	klass = PyObject_GetAttrString(mod, name_str);
 	if (klass == NULL) {
 		cPickle_ErrFormat(PicklingError,
-				  "Can't pickle %s: it's not found as %s.%s",
+				  "Can't pickle %s: attribute lookup %s.%s "
+				  "failed",
 				  "OSS", args, module, global_name);
 		goto finally;
 	}