When recipe mutate options, options values are written to .installed.cfg
without escaping buildout substitution syntax, so if a recipe sets an option
value that could be interpreted as a buildout substitution, it is written as is
in .installed.cfg.
This can be a problem if options read from _read_installed_part_options are
accessed, like it's the case with slapos patched buildout which saves
installed options after an error with part installation or after each part
installation when running in verbose mode.