create table fixer_rates_failure_responses (
  success boolean not null,
  error 
);
comment on table fixer_rates_failure_responses is '
  fixer.io failure response for exchange rate between two currencies
';

comment on column fixer_rates_failure_responses.success is '
  response status, should be false in this case
';
comment on column fixer_rates_failure_responses.error is '
  error from fixer.io
';