Non-utf8 PDF can't be lightweight-cleaned
A user reported privately that the following file can't be cleaned: fail_b_올해_상반기_한국_입국_탈북민_99명-향후_입국_추이_지켜봐야____RFA_자유아시아방송_Safari.pdf
$ mat2 ./mat2 -L ./fail\ b\ 올해\ 상반기\ 한국\ 입국\ 탈북민\ 99명-향후\ 입국\ 추이\ 지켜봐야”\ —\ RFA\ 자유아시아방송\ Safari.pdf
[-] ./fail b 올해 상반기 한국 입국 탈북민 99명-향후 입국 추이 지켜봐야” — RFA 자유아시아방송 Safari.pdf can't be cleaned: input string not valid UTF-8
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$
It seems that cairo/poppler do not like CJK stuff, sigh.