[docs] [issue15355] generator.__next__() docs should mention exception if already executing

[Chris Jerdonek]

Chris Jerdonek added the comment:

Terry, if when reviewing my patch for issue 15457, you also have time to review this much simpler patch (also in the documentation on generators), I would appreciate it.  If not, that's okay.

----------
nosy: +terry.reedy

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue15355>
_______________________________________