Being a part of "Stack Overflow in Russian" translation team I'm wondering why do some new strings not able to translate due to the lack in translation database?
As far as I know for the string surrounding it with the function like
tr("english string that needs to be translated") is enough to make it translatable (i.e. automatically placed as a source string into Transifex database). Hence, it should be not too hard to detect such strings on code review stage or even by auto-check before merging new commit into working branch.
Is there a way to prevent appearance of untranslatable strings (which should be translatable for localized sites) in SE code base?