Google Maps API - Sign Geocode Requests with Python 3 - google-maps-api-3

Question

I'm trying to create a script to generate signed urls using my Maps API license to geocode addresses, but I'm having trouble with my sign_url function.
import urllib
import urllib.parse
import base64
import hashlib
import hmac
import re
google_apis_url_http = 'http://maps.googleapis.com'
geocoding_endpoint_json = '/maps/api/geocode/json'
def encode_params(address, client, sensor):
return urllib.parse.urlencode({'address': address, 'client': client, 'sensor': sensor})
def sign_url(url, private_key):
decoded_key = base64.urlsafe_b64decode(private_key)
signature = hmac.new(decoded_key, url, hashlib.sha1)
encoded_signature = base64.urlsafe_b64encode(signature.digest())
return encoded_signature
with open("addresses.txt", "r") as inputFile:
inputList = inputFile.read().splitlines()
for line_address in inputList[0:1]:
comma_stripped_address = re.sub(",", "", line_address)
formatted_address = re.sub(" ", "+", comma_stripped_address)
encoded_params = encode_params(formatted_address, 'gme-********', 'false')
url_to_sign = geocoding_endpoint_json + '?' + encoded_params
print(sign_url(url_to_sign, '********'))
Here's the error I'm getting:
Traceback (most recent call last):
File "/Users/[me]/PycharmProjects/Google APIs/geocode_auth.py", line 31, in <module>
print(sign_url(url_to_sign, '********'))
File "/Users/[me]/PycharmProjects/Google APIs/geocode_auth.py", line 18, in sign_url
signature = hmac.new(decoded_key, url, hashlib.sha1)
File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/hmac.py", line 131, in new
return HMAC(key, msg, digestmod)
File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/hmac.py", line 73, in __init__
self.update(msg)
File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/hmac.py", line 79, in update
raise TypeError("expected bytes, but got %r" % type(msg).__name__)
TypeError: expected bytes, but got 'str'
Anyone know why this TypeError is being raised? I'm modeling the script off of a demo done in Python v2, so it's possible something broke in v3...