Euro (EUR) is not in self.supported_currencies

[dk-WZFinTech]

With definition of supported rates like:

    def __init__(self):
        """Populate supported currencies list."""
        rates = self.get_rates()['rates']
        self.supported_currencies = [cur for cur in rates]

'EUR' is omitted because is used as base here:

python-exchangeratesapi/exchangeratesapi/api.py

Line 23 in 86eed44

rates = self.get_rates()['rates']

then:

assert exchange_api.is_currency_supported('EUR')

will raise False.

My suggestion to solve it:

1. Remove supported_currencies variable from Api
2. Update is_currency_supported about base parameter:

    def is_currency_supported(self, currency, base='EUR'):
        """Populate supported currencies list."""
        rates = self.get_rates(base)['rates']
        supported_currencies = [cur for cur in rates]
        return currency in supported_currencies

3. Add test cases:

• assert exchange_api.is_currency_supported('EUR', base='USD)

• assert not exchange_api.is_currency_supported('EUR') -> https://exchangeratesapi.io/latest?base=EUR&symbols=EUR ends with 404 error