bug#33569: Missing sanitizing of '[]' in pypi-importer

[swedebugia]

E.g.
sdb@komputilo ~/guix-tree$ ~/guix-tree/pre-inst-env guix import pypi 
snakemake
...
  (propagated-inputs
    `(("python-[reports]"
       ,#{python-\x5b;reports\x5d;}#)
      ("python-appdirs" ,python-appdirs)
...
--
Cheers Swedebugia