unix-ffi/datetime: Add tzinfo.__new__ to make the package importable.

Add constructor to tzinfo class so that the package can be imported without
errors.

unix-ffi/datetime/datetime.py

@@ -958,6 +958,10 @@ class tzinfo:
 
     __slots__ = ()
 
+    def __new__(self, *args, **kwargs):
+        """Constructor."""
+        return object.__new__(self)
+
     def tzname(self, dt):
         "datetime -> string name of time zone."
         raise NotImplementedError("tzinfo subclass must override tzname()")