refactor ServerAdapter.__repr__()

"%r" placeholder exists at least from 2008
https://www.python.org/dev/peps/pep-3140/

bottle.py

@@ -3467,8 +3467,7 @@ def _listen_url(self):
             return "http://%s:%d/" % (self.host, self.port)
 
     def __repr__(self):
-        args = ', '.join('%s=%s' % (k, repr(v))
-                          for k, v in self.options.items())
+        args = ', '.join('%s=%r' % kv for kv in self.options.items())
         return "%s(%s)" % (self.__class__.__name__, args)