Calling `load_tasks` in several files made rails load the tasks several
times, and so they were executed several times when called.
Since the milestone migration can't be executed twice in a row (it would
fail with duplicated ID records), loading the tasks several times made
the milestone migrations task specs fail.
Ruby can't have hyphens in method names, so sending something like
`record.title_pt-BR` would raise an exception.
Using globalize's `localized_attr_name_for` method fixes the bug.
Thanks Marko for the tip.
We think aborting the migration will generate more headaches to system
administrators, who will have to manually check and fix every invalid
record before anything can be migrated.
