Invalid Language field in DESCRIPTION file

[ellessenne]

From CRAN:

Dear maintainer,

This has a DESCRIPTION file with an invalid Language field.

According to 'Writing R Extensions',

  A ‘Language’ field can be used to indicate if the package
  documentation is not in English: this should be a comma-separated list
  of standard (not private use or grandfathered) IETF language tags as
  currently defined by RFC 5646 (<https://www.rfc-editor.org/rfc/rfc5646>,
  see also <https://en.wikipedia.org/wiki/IETF_language_tag>), i.e., use
  language subtags which in essence are 2-letter ISO 639-1
  (<https://en.wikipedia.org/wiki/ISO_639-1>) or 3-letter ISO 639-3
  (<https://en.wikipedia.org/wiki/ISO_639-3>) language codes.

So e.g. en_US or en_GB are invalid, and should be replaced by en-US or
en-GB, respectively.