python error running make doc

[Federico Bruni]

Fedora 31. /usr/bin/python points to version 3.7.6.
I'm running `make doc` in the translation branch and I get this error:

$ make -j3 doc
GNUmakefile:30: warning: overriding recipe for target 'po-update'
/home/fede/src/lilypond-translation/stepmake/stepmake/podir-targets.make:14: 
warning: ignoring old recipe for target 'po-update'
Making Documentation/po/out-www/messages (hard links)
Making input/regression/out-www/collated-files.list < 1359 files
Making input/regression/out-www/version.itexi
Making input/regression/out-www/weblinks.itexi
Making input/regression/out-www/AAA-intro-regression.texi < tely
Making input/regression/out-www/collated-files.tely
Making input/regression/out-www/collated-files.texi < tely
Traceback (most recent call last):
 File "../../scripts/lilypond-book.py", line 69, in <module>
   import lilylib as ly
 File "/home/fede/src/lilypond-translation/python/lilylib.py", line 169
   print('command failed:', cmd, file=sys.stderr)
                                     ^
SyntaxError: invalid syntax
make[3]: *** [../../make/ly-rules.make:25: 
out-www/AAA-intro-regression.texi] Error 1
make[3]: *** Waiting for unfinished jobs....
Traceback (most recent call last):
 File "../../scripts/lilypond-book.py", line 69, in <module>
   import lilylib as ly
 File "/home/fede/src/lilypond-translation/python/lilylib.py", line 169
   print('command failed:', cmd, file=sys.stderr)
                                     ^
SyntaxError: invalid syntax
make[3]: *** [../../make/ly-rules.make:36: out-www/collated-files.texi] 
Error 1
Traceback (most recent call last):
 File 
"/home/fede/src/lilypond-translation/scripts/build/create-weblinks-itexi.py", 
line 601, in <module>
   make_download_source("downloadStableSource", VERSION_STABLE, lang)
 File 
"/home/fede/src/lilypond-translation/scripts/build/create-weblinks-itexi.py", 
line 453, in make_download_source
   make_macro(macroLang(name,lang), string)
 File 
"/home/fede/src/lilypond-translation/scripts/build/create-weblinks-itexi.py", 
line 428, in make_macro
   print(string.encode('utf-8'))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 
75: ordinal not in range(128)
make[3]: *** 
[/home/fede/src/lilypond-translation/stepmake/stepmake/texinfo-rules.make:126: 
out-www/weblinks.itexi] Error 1
make[3]: *** Deleting file 'out-www/weblinks.itexi'
make[2]: *** 
[/home/fede/src/lilypond-translation/stepmake/stepmake/generic-targets.make:167: 
WWW-1] Error 2
make[1]: *** 
[/home/fede/src/lilypond-translation/stepmake/stepmake/generic-targets.make:167: 
WWW-1] Error 2
make: *** 
[/home/fede/src/lilypond-translation/stepmake/stepmake/generic-targets.make:185: 
doc-stage-1] Error 2