google-cloud-spanner 0.27.0

Features

• Breaking: Session.run_in_transaction returns the callback's return value
  instead of the committed timestamp. (#3753)
• Block creation of transaction for Session with existing transaction. (#3785)
• Breaking: Remove Database.read and Database.execute_sql convenience methods. (#3787)
• Add a .one and .one_or_none method on StreamedResultSet. (#3784)

Implementation

• Make __eq__ and __ne__ work correctly with "unknown" types. (#3765)
• Bug-fix: Re-use explicit credentials when creating database.spanner_api. (#3722)
  commit fe757be
• Bug-fix: Catch both a GaxError and _Rendezvous (from grpcio) for failures in run_in_transaction (#3663)
• Prevent nested transactions. (#3789)

Docs

• Improve the Spanner README. (#3791, #3796)
• Drop Session as a promoted, top-level entity in docs. (#3792)

Dependencies

• Updating google-cloud-core ~= 0.27 (#3864)
• google.cloud.iterator moved to google.api.core.page_iterator (#3770)
• Using google.api.core.future instead of google.cloud.future (#3764)

PyPI: https://pypi.org/project/google-cloud-spanner/0.27.0/