locations: beware of utf-8
Our locations (in Bison) consider 1 bytes = 1 character. As a result:
# Invalid context.
xfail(r'''digraph
{
vcsn_context = "[...]? → unknown"
}
''', r'''3.18-37: expected weightset here:
[...]? → unknown
^_
vcsn_context = "[...]? → unknown"
^^^^^^^^^^^^^^^^^^^^
while reading automaton''')
The first caret is too far, the second carets are too many.