The currency code is invalid and does not follow ISO 4217.
The currency code is not supported.
The currency code already exists. When creating an exchange rate, its currency should not be
associated with any existing exchange rate. When creating a list of exchange rates, there
should not be two exchange rates associated with same currency.
The exchange rate value is invalid. When the ExchangeRate.refreshRate is
ExchangeRateRefreshRate.FIXED, the ExchangeRate.exchangeRate should be larger
than 0. Otherwise it is invalid.
The exchange rate value is not found. When the ExchangeRate.refreshRate is
ExchangeRateRefreshRate.DAILY or ExchangeRateRefreshRate.MONTHLY, the
ExchangeRate.exchangeRate should be assigned by Google. It is not found if Google
cannot find such an exchange rate.
The value returned if the actual value is not exposed by the requested API version.