Making bucket level access default

[sverrirarnors]

After having set up authentication with bucket level permissions (which is now the default and recommended way to authenticate to GCS), the library always returns this warning:

http_400 Cannot insert legacy ACL for an object when uniform bucket-level access is enabled. 
Read more at https://cloud.google.com/storage/docs/uniform-bucket-level-access - Retrying with predefinedAcl='bucketLevel'

which then works.

Could it be a good idea to have bucket level permissions be the default ones? Then one would not have to explicitly set the predefinedAcl all the time. This would be very convenient when working with other libraries, such as pins.