TMX files with non-ISO language codes cannot be imported

We have been faced with customers not being able to import certain TMX translation memories. This is because these do not contain valid ISO language codes.

Before importing a TMX, be sure to double check that no node in the TMX does contain invalid codes. For example, if the language in question is English (US), an attribute such as xml:lang="en-US" would be valid, since EN-us is a valid ISO code; on the contrary, an attribute such as  xml:Lang="engl-US" would generate an import error, since that is not a  valid ISO code.