Fixes now in trunk and release26-maint.

Note that RotatingFileHandler will open the file when shouldRollover()
is called - which it is from emit() - and doRollover() will also open
the file even if a delay parameter is set.

TimedRotatingFileHandler will not open a file if delay is set until
rollover actually occurs, as shouldRollover goes by time only rather
than file size.

The delay parameter is intended only as a hint to the handlers to delay
opening until as long as possible, and they will try to honour this as
far as is practicable.