Import doesn't work if the GTFS data is updated

[werebus]

rake aborted!
ActiveRecord::RecordInvalid: Validation failed: Hastus has already been taken
/home/matt/projects/bojangles/lib/models/service.rb:20:in `block in import'
/home/matt/projects/bojangles/lib/models/service.rb:19:in `each'
/home/matt/projects/bojangles/lib/models/service.rb:19:in `import'
/home/matt/projects/bojangles/lib/bojangles.rb:31:in `prepare'
/home/matt/projects/bojangles/Rakefile:9:in `block (2 levels) in <top (required)>'

The service is "new" because something other than hastus_id changed:

https://github.com/umts/bojangles/blob/e1d3cf5950e6bd0211be9ceda1bd87e7a57e8cb2/lib/models/service.rb#L20

But the validation fails:

https://github.com/umts/bojangles/blob/e1d3cf5950e6bd0211be9ceda1bd87e7a57e8cb2/lib/models/service.rb#L7