Error when language is pt-BR because of '-'. Maybe adding sep param to get_locale?

[wesleyfralima]

Hey, thanks for the great job. I just started using flask-babel and it's been a blast!

I got an error, could you help me to solve it in a proper way?

My browser is set to Brazilian Portuguese and seems like it sends the info 'pt-BR'. But, sadly, the app crashes with the following error:

ValueError: expected only letters, got 'pt-br'

I read a little bit of the Babel's code and realised that get_locale calls Locale.parse. Locale.parse accepts a sep parameter, but seems it is not being used here (because get_locale itself does not pass it nor accepts a sep parameter).

I edited get_locale like the following and it worked:

Line 250 for me:
It is: def get_locale() -> Optional[Locale]: ...
I made: def get_locale(sep: str = None) -> Optional[Locale]: ...

Line 268 for me (still get_locale):
It is: locale = Locale.parse(rv)
I made: locale = Locale.parse(rv, sep=sep)

Is this a bug or is it me who can't use the code properly?

Thank you in advance!