TypeError: must be str, not bytes

[Zhsv]

line 33:

requestContentBase64String = base64.b64encode(m.digest()).decode('utf-8')

Thank You very much!
Now a new error

Traceback (most recent call last):
File "C:/Cloud/Cripto/3.py", line 53, in <module>
print (api_query("GetBalance"))
File "C:/Cloud/Cripto/3.py", line 35, in api_query
hmacsignature = base64.b64encode(hmac.new(base64.b64decode( API_SECRET ), signature, hashlib.sha256).digest())
File "C:\Users\Сергей\AppData\Local\Programs\Python\Python36-32\lib\base64.py", line 87, in b64decode
return binascii.a2b_base64(s)
binascii.Error: Incorrect padding