Comment 0 for bug 963460

In Precise, using check-language-support -l zh_CN returns:
cmap-adobe-gb1 firefox-locale-zh-hans fonts-arphic-uming ibus-sunpinyin ibus-table-wubi language-pack-gnome-zh-hans language-pack-zh-hans libreoffice-help-zh-cn libreoffice-l10n-zh-cn poppler-data thunderbird-locale-zh-cn thunderbird-locale-zh-hans ttf-arphic-ukai ttf-wqy-zenhei

whereas check-language-support zh-hans returns:
cmap-adobe-gb1 firefox-locale-zh-hans fonts-arphic-uming ibus-sunpinyin ibus-table-wubi language-pack-gnome-zh-hans language-pack-zh-hans poppler-data thunderbird-locale-zh-hans ttf-arphic-ukai ttf-wqy-zenhei

You will notice that zh-hans does not have any of the *-zh-cn packages listed. This is an issue because in situations where you want to install zh_CN language/locale support using Ubiquity, Ubiquity will automatically convert zh_CN to zh-hans and then only install those packages.

The same is true for zh_TW and zh-hant where the *-zh-tw will not be installed if the user chooses zh_TW.