bug#13008: Invalid oct number convertion in string

[nalaginrut]

Here is the story:
=====================cut===============================
scheme@(guile-user)> (format #t "\033[32;31mhello\033[5m")
33[32;31mhello33[5m$2 = #t
scheme@(guile-user)> (format #t "\x1b[32;31mhello\x1b[5m")
hello (in red color)
=====================end===============================

Seems "\033" can't be converted to "\x1b", and I tried "\o1b" failed.
I believe it ought to be a bug.