On MySQL, the sources table gets created with a full text index in the 20101018120603_create_sources.rb migration:

CreateSources: migrating ==================================================
-- create_table(:sources)
   > 0.2536s
- execute("ALTER TABLE sources ENGINE = MYISAM")
   > 0.1248s
- execute("ALTER TABLE sources ADD FULLTEXT (value)")
   -> 0.0606s
CreateSources: migrated (0.4396s) =========================================

db/schema.rb gets written out as:

create_table "sources", :force => true do |t|
    t.text "value" 
  end
  add_index "sources", ["value"], :name => "value"

However when this is run as part of loading test fixtures, it fails as it doesn't create a full text index:

CREATE TABLE `sources` (`id` int(11) DEFAULT NULL auto_increment PRIMARY KEY, `value` text) ENGINE=InnoDB
CREATE INDEX `value` ON `sources` (`value`)^[[0m
Mysql::Error: BLOB/TEXT column 'value' used in key specification without a key length: CREATE  INDEX `value` ON `sources` (`value`)

I'd suggest the same fix used for #2126 is applied to sources, or change it to use a SQL schema.