Revert "gh-69714: Remove unreachable code (and increase test coverage)"

This reverts commit a96786c.

Author: bxsx

Lib/calendar.py

@@ -555,6 +555,8 @@ def __enter__(self):
         _locale.setlocale(_locale.LC_TIME, self.locale)
 
     def __exit__(self, *args):
+        if self.oldlocale is None:
+            return
         _locale.setlocale(_locale.LC_TIME, self.oldlocale)