This is pdfTeX, Version 3.14159265-2.6-1.40.19 (TeX Live 2019/dev/Debian) (preloaded format=pdflatex 2020.1.6)  26 APR 2020 17:33
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**exercice_fr.tex
(./exercice_fr.tex
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! LaTeX Error: File `lmodern.sty' not found.

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: sty)

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l.6 \usepackage
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Here is how much of TeX's memory you used:
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!  ==> Fatal error occurred, no output PDF file produced!