Remove fancy unpacking

Author: haard

src/pythonjsonlogger/jsonlogger.py

@@ -133,7 +133,7 @@ def _str_to_fn(self, fn_as_str):
         if not isinstance(fn_as_str, str):
             return fn_as_str
 
-        *path, function = fn_as_str.split('.')
+        path, _, function = fn_as_str.rpartition('.')
         module = importlib.import_module('.'.join(path))
         return getattr(module, function)