Jason Spencer added the comment:
Then I would argue that it is at least a documentation bug. The 3.6 format
spec mini language still claims that {} is equivalent to {:s}, which now is
only conditionally true.
I would also argue that having different behavior for {} and {:s}, which
are
New submission from Jason Spencer :
Objects with __str__ but WITHOUT __format__ are string-convertible and
default-to-str formattable. But the explicit use of '{:s}' as a format string
fails to format these objects as expected. Either it is no longer the case
that '{}&
