Update logging-cookbook to prefixmatch

Author: hugovk

Doc/howto/logging-cookbook.rst

@@ -3877,7 +3877,7 @@ subclassed handler which looks something like this::
         def format(self, record):
             version = 1
             asctime = dt.datetime.fromtimestamp(record.created).isoformat()
-            m = self.tz_offset.match(time.strftime('%z'))
+            m = self.tz_offset.prefixmatch(time.strftime('%z'))
             has_offset = False
             if m and time.timezone:
                 hrs, mins = m.groups()