I'm not sure whether this is a bug or a feature request, but it seems as though the following should produce the same result:

In [1]: 'a' + 'b' + 'c'
Out[1]: 'abc'

In [2]: sum(('a', 'b', 'c'))
TypeError Traceback (most recent call last)
in
----> 1 sum(('a', 'b', 'c'))

TypeError: unsupported operand type(s) for +: 'int' and 'str'

The error message is confusing (there is no integer).