Using the python coinbase API-- The functions-- get_buy_price, get_sell_price, get_spot_price, get_historical_data, etc... all seem to return bitcoin prices only. Is there a way of querying Ethereum prices? 
It would seem that currency_pair = 'BTC-USD' could be changed to something akin to currency_pair = 'ETH-USD' although this has no effect.
I would expect that the API simply doesn't support this, except that the official documentation explicitly states: 

Get the total price to buy one bitcoin or ether 

I can work around this somewhat by using the quote='true' flag in the buy/sell request. This however only works moving forward, I would like historical data.
Something worked for me with a similar problem calling exchange rates.
Try changing the params in 

coinbase\wallet\client.py

from 

response = self._get('v2', 'prices', 'spot', data=params)

to

response = self._get('v2', 'prices', 'spot', params=params)
Historical ethereum prices - Coinbase API