Cannot add locale CP1215 (lowcase)

[Terentev-mn]

I try add locale via saltstack. In salt's module locale name is normalizing, and
it will transform from 'CP1251' to 'cp1215'
When I tried aaply state, I got error:
# Error: 'ru_RU.cp1251' is not a supported language or locale

Then I try manual do the same..
~# locale-gen ru_RU.cp1251
Error: 'ru_RU.cp1251' is not a supported language or locale
But upper case, all fine
~# locale-gen ru_RU.CP1251
Generating locales (this might take a while)...
  ru_RU.CP1251... done
Generation complete.

This affected on Ubuntu 16.04, 18.04

[Gunnar Hjalmarsson (gunnarhj)]

Yes, the locale-gen script requires that you use the real name according to /usr/share/i18n/SUPPORTED. But once ru_RU.CP1251 has been generated, glibc recognizes both ru_RU.CP1251 and the alias ru_RU.cp1251. For instance you can confirm it with:

locale -a | grep ru