Package babel Error: Unknown language `francais'

I updated TexLive today, and it has updated French language successfully according to the utility:

However I have a typesetting problem that did not appear before, with the command
usepackage[francais]{babel}

Namely
./struct_effectivite.tex:112: Package babel Error: Unknown language `francais’.
Either you have
(babel) misspelled its name, it has not been installed,
(babel) or you requested it in a previous run. Fix its name,
(babel) install it or just rerun the file, respectively. In
(babel) some cases, you may need to remove the aux file.
See the babel package documentation for explanation.
Type H for immediate help.

Note that the same error message appears if I put instead
usepackage[french]{babel}
(literally! It says Unknown language ‘francais’ and not Unknown language ‘french’).

How can I correct this problem?

Upon request, here is an example with its log file:

documentclass[12pt]{smfart}
usepackage{amscd,verbatim}
usepackage[french]{babel}
usepackage[latin1]{inputenc}
usepackage[T1]{fontenc}

begin{document}

Bla bla bla.

end{document} 

This is pdfTeX, Version 3.14159265-2.6-1.40.21 (TeX Live 2020) (preloaded format=pdflatex)
 write18 enabled.
entering extended mode
(./test-babel.tex
LaTeX2e <2020-10-01> patch level 2
L3 programming layer <2020-10-27> xparse <2020-03-03>
(/Users/kahn/Library/texmf/tex/latex/smfart.cls
Document Class: smfart 2000/11/20 v1.3 Classe LaTeX pour les articles publies p
ar la SMF
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amsgen.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsfonts/amsfonts.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amsmath.sty
For additional information on amsmath, use the `?' option.
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amstext.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amsbsy.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amsopn.sty))
(/usr/local/texlive/2020/texmf-dist/tex/latex/tools/multicol.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/amscls/amsthm.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsfonts/umsa.fd)
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsfonts/umsb.fd))
(/usr/local/texlive/2020/texmf-dist/tex/latex/amsmath/amscd.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/tools/verbatim.sty)
(/usr/local/texlive/2020/texmf-dist/tex/generic/babel/babel.sty
(/usr/local/texlive/2020/texmf-dist/tex/generic/babel/babel.def
(/usr/local/texlive/2020/texmf-dist/tex/generic/babel/txtbabel.def))
(/usr/local/texlive/2020/texmf-dist/tex/generic/babel-french/french.ldf))
(/usr/local/texlive/2020/texmf-dist/tex/latex/carlisle/scalefnt.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/graphics/keyval.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/base/inputenc.sty
(/usr/local/texlive/2020/texmf-dist/tex/latex/base/latin1.def))
(/usr/local/texlive/2020/texmf-dist/tex/latex/base/fontenc.sty)
(/usr/local/texlive/2020/texmf-dist/tex/latex/l3backend/l3backend-pdftex.def)
(./test-babel.aux)

./test-babel.tex:7: Package babel Error: Unknown language `francais'. Either yo
u have
(babel)                misspelled its name, it has not been installed,
(babel)                or you requested it in a previous run. Fix its name,
(babel)                install it or just rerun the file, respectively. In
(babel)                some cases, you may need to remove the aux file.

See the babel package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.7 begin{document}
                    
? 
[1{/usr/local/texlive/2020/texmf-var/fonts/map/pdftex/updmap/pdftex.map}]
(./test-babel.aux) ){/usr/local/texlive/2020/texmf-dist/fonts/enc/dvips/cm-supe
r/cm-super-t1.enc}</usr/local/texlive/2020/texmf-dist/fonts/type1/public/cm-sup
er/sfrm0900.pfb></usr/local/texlive/2020/texmf-dist/fonts/type1/public/cm-super
/sfrm1200.pfb>
Output written on test-babel.pdf (1 page, 12148 bytes).
SyncTeX written on test-babel.synctex.gz.
Transcript written on test-babel.log.