This is my locale.gen

# This file names the list of locales to be built when glibc is installed.
# The format is <locale>/<charmap>, where <locale> is a locale from the
# /usr/share/i18n/locales directory, and <charmap> is name of one of the files
# in /usr/share/i18n/charmaps/. All blank lines and lines starting with # are
# ignored. Here is an example:
# en_US/ISO-8859-1

en_US.UTF-8/UTF-8
es_AR.UTF-/UTF-8

#en_US/ISO-8859-1
#ja_JP.EUC-JP/EUC-JP
#ja_JP.UTF-8/UTF-8
#ja_JP/EUC-JP
#en_HK/ISO-8859-1
#en_PH/ISO-8859-1
#de_DE/ISO-8859-1
#de_DE@euro/ISO-8859-15
#es_MX/ISO-8859-1
#fa_IR/UTF-8
#fr_FR/ISO-8859-1
#fr_FR@euro/ISO-8859-15
#it_IT/ISO-8859-1



And this is what I get when running locale-gen

 * Generating 1 locales (this might take a while)
 *  (1/1) Generating es_AR.UTF-/UTF-8 ...
/usr/share/i18n/locales/es_AR:26: LC_IDENTIFICATION: unknown character in field `address'
/usr/share/i18n/locales/es_AR:89: LC_TIME: unknown character in field `abday'
/usr/share/i18n/locales/es_AR:91: LC_TIME: unknown character in field `abday'
/usr/share/i18n/locales/es_AR:95: LC_TIME: unknown character in field `day'
/usr/share/i18n/locales/es_AR:98: LC_TIME: unknown character in field `day'
cannot write output files to `(null)': No such file or directory                                                                                           [ !! ]
 * Generation complete