[eesmith]

A quick look at the Python stdlib gives shows some of the breakage that would occur:

1) existing uses of .format() would break:

   aifc.py: raise Error('marker {0!r} does not exist'.format(id))

2) existing uses of "%" formatting would break:

    argparse.py: result = '{%s}' % ','.join(choice_strs)

3) many regular expressions would break:

    uuid.py: if re.fullmatch('(?:[0-9a-f][0-9a-f]-){5}[0-9a-f][0-9a-f]', value):

4) existing strings which contain uuids would break:

    uuid.py: >>> x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')