Why is this an issue?
FIXME tags are commonly used to mark places where a bug is suspected, but which the developer wants to deal with later.
Sometimes the developer will not have the time or will simply forget to get back to that tag.
This rule is meant to track those tags and to ensure that they do not go unnoticed.
Noncompliant code example
CREATE TABLE notnull(col1 INTEGER NOT NULL)
INSERT notnull VALUES (@value) -- FIXME ensure @value is not null