Launchpad currently recommends translating gnome-session in Ubuntu Cosmic.

Template "gnome-session-3.0" in Ubuntu Cosmic package "gnome-session"

Language Status Untranslated Need review Changed Last Edited By
Cherokee 100.00  100.0% untranslated 87 87 0 0
Dakota 100.00  100.0% untranslated 87 87 0 0
Hawaiian 100.00  100.0% untranslated 87 87 0 0
Inuktitut 100.00  100.0% untranslated 87 87 0 0
Lakota 100.00  100.0% untranslated 87 87 0 0
Ojibwe 100.00  100.0% untranslated 87 87 0 0
Spanish 000.00  100.0% translated 0 0 8 8 2018-09-10 12:19:50 UTC 2018-09-10 Rodrigo
Tlingit 100.00  100.0% untranslated 87 87 0 0
Yiddish 100.00  100.0% untranslated 87 87 0 0
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Key to this table: “Unchanged” means Translated
and “untranslated” means just that, Untranslated

Other versions of gnome-session in Ubuntu