Merge pull request matplotlib#3107 from choffmann/fix-issue-3106

Bug-fix for issue 3106

Author: tacaswell

lib/matplotlib/docstring.py

@@ -87,7 +87,7 @@ def __init__(self, addendum, join=''):
 
     def __call__(self, func):
         docitems = [func.__doc__, self.addendum]
-        func.__doc__ = func.__doc__ and ''.join(docitems)
+        func.__doc__ = func.__doc__ and self.join.join(docitems)
         return func