Allow a different locale separator than underscore

[Sundava]

In the get_locale function, the locale is sent to babel for parsing with no optional arguments. This means the call to Locale.parse(rv) (defined here in python-babel) uses the default value of _ as a separator.

However, RFC 5646 which is part of BCP 47 preconises using a hyphen (-) as a separator between the language tag and the subtag.

Is it possible to allow some configuration as to what separator is used in the call to Locale.parse ?