Symfony version(s) affected: 3.4

When we generate the list of language names for the Intl component we rely on https://github.com/unicode-org/icu/blob/master/icu4c/source/data/lang/en.txt

This provides many translations, but is not the authoritative code list as-is.

See e.g. no and sh

• https://github.com/unicode-org/icu/blob/master/icu4c/source/data/lang/en.txt#L438
• https://github.com/unicode-org/icu/blob/master/icu4c/source/data/lang/en.txt#L531

which are marked legacy in the metadata file, respectively

• https://github.com/unicode-org/icu/blob/master/icu4c/source/data/misc/metadata.txt#L1018
• https://github.com/unicode-org/icu/blob/master/icu4c/source/data/misc/metadata.txt#L1234

The problem comes with ISO vs. ICU. ISO qualifies e.g. no a macrolanguage (https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes) and seems valid today: https://www.loc.gov/standards/iso639-2/php/langcodes_name.php?iso_639_1=no, but sh is not: https://www.loc.gov/standards/iso639-2/php/langcodes_name.php?iso_639_1=sh

Not sure what to do :) Issue for now, to move forward in #33140

For now this causes the list to (alpha2 vs alpha3) to vary so it seems.