That's true. Now I have finde the reason.

Someone has changed a function in lib/python3.5/string.py : _vformat.
This function returns now a tuple (befor it was only one return value).

IPython inherits from this object in lib/python3.5/site-packages/IPython/utils/text.py
Because of this change the IPython code is not working.

It seems to me, that this change in python is not nessesary.

I don't, know how to find the commit, message who has changed this and why.



Python 3.5.0:
def _vformat( ..., auto_arg_index=0):
    ...
    format_spec = self._vformat( ..., auto_arg_index=auto_arg_index)
    ...
    return ''.join(result)

Python 3.5.1:
def _vformat( ..., auto_arg_index=0):
    ...
    format_spec, auto_arg_index = self._vformat( ..., auto_arg_index=auto_arg_index)
    ...
    return ''.join(result), auto_arg_index