[ccxt] fix unsupported fiat failures (#620)

* prepare to support FIAT/Crypto trading

* Don't fail fiat-convert for unsupported stake currencies

* remove commented code

* Add BNB to cryptomap

* Fix test-failure

* related to random execution as fee was not properly mocked if this is
one of the first tests

freqtrade/tests/optimize/test_backtesting.py

@@ -287,11 +287,12 @@ def test_setup_configuration_with_arguments(mocker, default_conf, caplog) -> Non
     )
 
 
-def test_start(mocker, init_backtesting, default_conf, caplog) -> None:
+def test_start(mocker, init_backtesting, fee, default_conf, caplog) -> None:
     """
     Test start() function
     """
     start_mock = MagicMock()
+    mocker.patch('freqtrade.exchange.get_fee', fee)
     mocker.patch('freqtrade.optimize.backtesting.Backtesting.start', start_mock)
     mocker.patch('freqtrade.configuration.open', mocker.mock_open(
         read_data=json.dumps(default_conf)

freqtrade/tests/test_fiat_convert.py

@@ -77,8 +77,7 @@ def test_fiat_convert_find_price(mocker):
     with pytest.raises(ValueError, match=r'The fiat ABC is not supported.'):
         fiat_convert._find_price(crypto_symbol='BTC', fiat_symbol='ABC')
 
-    with pytest.raises(ValueError, match=r'The crypto symbol XRP is not supported.'):
-        fiat_convert.get_price(crypto_symbol='XRP', fiat_symbol='USD')
+    assert fiat_convert.get_price(crypto_symbol='XRP', fiat_symbol='USD') == 0.0
 
     mocker.patch('freqtrade.fiat_convert.CryptoToFiatConverter._find_price', return_value=12345.0)
     assert fiat_convert.get_price(crypto_symbol='BTC', fiat_symbol='USD') == 12345.0