try specifying keys manually
s3 = boto3.resource('s3',
aws_access_key_id=ACCESS_ID,
aws_secret_access_key= ACCESS_KEY)
Make sure you don't include your ACCESS_ID and ACCESS_KEY in the code directly for security concerns. Consider using environment configs and injecting them in the code as suggested by @Tiger_Mike.
For Prod environments consider using rotating access keys: https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html#Using_RotateAccessKey