Merge pull request #5959 from gandalf013/master

BUG: use the "join" string in Appender decorator

Author: y-p

pandas/util/decorators.py

@@ -102,7 +102,7 @@ def __call__(self, func):
         func.__doc__ = func.__doc__ if func.__doc__ else ''
         self.addendum = self.addendum if self.addendum else ''
         docitems = [func.__doc__, self.addendum]
-        func.__doc__ = ''.join(docitems)
+        func.__doc__ = self.join.join(docitems)
         return func