test_main_invalid_unicode() of test_sys: print string as ascii

There are buildbot failures on "x86 FreeBSD 3.x" and "sparc solaris10 gcc 3.x".
I suppose that _Py_char2wchar() doesn't fail even if the locale encoding is
unable to decode the byte string, because _Py_char2wchar() has a special mode
for platform without mbrtowc() (ISO C99) function.

Let's check my theory by avoid error on the Python print() instruction.