Error 55 (language) should be changed from ERROR to WARNING

[mcplanner-zz]

Describe the bug
Error code 55 appears to require that the language in agency.agency_lang matches feed_info.feed_lang. Agency_lang is optional, so this appears to be an erroneous error.

To Reproduce
Run the validator on the following dataset: http://api.511.org/transit/datafeeds?api_key=[key]&operator_id=BA

Expected behavior
No notice should be generated in this case.

Witnessed behavior
This error message was included in the validator results.

Notice{filename='feed_info.txt', level='ERROR', code='55', title='Mismatching feed and agency language fields', description='Agency `agency_name`: `Bay Area Rapid Transit` has mismatching `agency.agency_lang`: `null` and feed_info.feed_lang`: `en`.', extra='{feedInfoFeedLang=en, agencyAgencyLang=null, agencyName=Bay Area Rapid Transit}'}]

Environment used

• OS: macOS Catalina 10.15.6
• Java version: 11.0.5
• gtfs-validator version: v1.2.2

Additional context
None

[ghost]

@Cristhian-HA :

• create issue type 'community' (type 2) for help setting up the dataset on GitHub (@antrim)
  https://github.com/MobilityData/gtfs-validator/issues/new?assignees=&labels=community&template=community.md&title=I+need+support+from+the+community+to...

@Fabrice-V :

• go through the procedure qith @timMillet at 17:00 EST today to add it to our end to end

[lionel-nj]

Related issue for v2 architecture in terms of re-introducing the concept of errors vs warnings - #549.

[lionel-nj]

Will be closed by #726. This has been set to be a WARNING instead of an ERROR.

[aababilov]

This issue is outdated. GTFS Validator does not show any notice in that case after #711