Update French postal codes for department from 1 to 9 without a leading 0.
user
```ruby
class UpdateFrenchPostalCodes < ActiveRecord::Migration
  def change
  	locations_count = Location.where(:name => "France")
			.first
			.children
			.where("locations.postal_code_prefix ~ '^.{4}$' ").count

		puts "Updating #{locations_count} locations."
    @bar = RakeProgressbar.new(locations_count)
  	(1..9).each do |num|
  		Location.where(:name => "France")
  			.first
  			.children
  			.where("locations.postal_code_prefix ~ '^#{num}.{3}$' ").each do |departement|
  				departement.update_attribute :postal_code_prefix, "0" + departement.postal_code_prefix
  				@bar.inc
  			end
  	end
  	@bar.finished
  end
end
```
assistant