- Correct Requires to googleapis-common-protos.
- Add Requires on python-google-filesystem, and stop including a file it
now ships.

- Update to 1.38.0:
- add getters and setters for encryption_key and kms_key_name
- retry auth.TransportError errors
- revise docstrings for generate_signed_url
- Ensure consistency check in test runs even if expected error
occurs
- silence expected errors for routine operations on BlobReader
- add blob.open() for file-like I/O
- update user_project usage and documentation in bucket/client
class methods
- update batch connection to request api endpoint info from
client
- allow metadata keys to be cleared
- allow signed url version v4 without signed credentials
- correctly encode bytes for V2 signature
- add mtls support
- correctly decode times without microseconds
- expose num_retries parameter for blob upload methods
- pass the unused parameter
- set custom_time on uploads
- address incorrect usage of request preconditions
- Amend default retry behavior for bucket operations on client
- support ConnectionError retries for media operations
- make retry parameter public and added in other methods
- avoid triggering global logging config
- fall back to 'charset' of 'content_type' in