The system check LongErrorMessage-boxes were missing the bottom border making them look a bit weird:

There is unfortunately a pretty specific rule from another part of Matomo:

table.entityTable tbody tr td {
     border-bottom: 1px solid #f2f2f2 !important;
}

so to make this look correct I also had to make the error rule more specific.
Hopefully the .error class is used nowhere else in Matomo

But I think it should be fine as it is generally defined here:

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done see checklist
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed