Accessibility concerns

Problem/Motivation

The SiteImprove accessibility checker flags the user-provided content of the sitewide alert and says:

All perceivable text content should be included in an ARIA landmark

Steps to reproduce

1. Install sidewide alert module
2. Install SiteImprove browser extension
3. Add and display sitewide alert content
4. Run SiteImprove browser extension

Proposed resolution

I'm not entirely sure what is appropriate here. I'm thinking possibly giving the outermost div in the sitewide alert template a role="banner" since it doesn't rise to the level of a role="alert" or role="alertdialog". I think it's up for discussion and possibly completely depends on what exactly will satisfy SiteImprove in particular.

I didn't see any other accessibility issues raised in the issue queue, so I'm wondering if there have ever been any checks done on this either by the maintainer or users.