Updated frequency error check

tests/test_tiingo.py

@@ -6,6 +6,7 @@ from unittest import TestCase
 import vcr
 
 from tiingo import TiingoClient
+from tiingo.api import InvalidFrequencyError
 from tiingo.restclient import RestClientError
 
 
@@ -124,6 +125,13 @@ class TestTickerPrices(TestCase):
         assert len(tickers) > 1
         assert all(ticker['assetType'] == 'ETF' for ticker in tickers)
 
+    def test_invalid_frequency_error(self):
+        with self.assertRaises(InvalidFrequencyError):
+            prices = self._client.get_ticker_price("GOOGL",
+                                                   startDate="2018-01-02",
+                                                   endDate="2018-01-02",
+                                                   frequency="1.5mins")
+
 # tiingo/news
 class TestNews(TestCase):