YAML content like the following one produced an error, because the
multi-line ScalarToken ends at the beginning of the 4th line (the one
with the value):
? >
multi-line
key
: value
Using either 'yes', 'no' or 'whatever', the user will be able to choose
whether to force block sequence items to be indented, to force them not
to be indented, or don't care, respectively.
