hstore default not properly recognized on rails 4.2

[morgoth]

There is ticket about changing format on rails 4.2 #212
Additionally it not properly recognize default value of hstore column:

-#  payment_failed_log                  :hstore           default({}), not null
+#  payment_failed_log                  :hstore           default(""), not null

[morgoth]

Actually this is how it works in PostreSQL - ""::hstore is the default that gives {} in Rails, so I'm not sure if we should do anything about it.
From my structure.sql:

...
my_hstore_column hstore DEFAULT ''::hstore NOT NULL,
...