chore: onboard to librarian

[ohmayr]

Towards googleapis/librarian#2460

[parthea]

As per offline discussion, here is an updated remove_regex

[rahul2393]

@parthea @ohmayr Is this good to merge?

[parthea]

Please could you check if librarian release stage is working?

I encountered the following error

Traceback (most recent call last):
  File "/app/./cli.py", line 1497, in handle_release_stage
    _update_version_for_library(repo, output, path_to_library, version)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/./cli.py", line 1234, in _update_version_for_library
    updated_content = _process_version_file(
        _read_text_file(version_file), version, version_file
    )
  File "/app/./cli.py", line 1168, in _process_version_file
    raise ValueError(
        f"Could not find version string in {version_path}. File was not modified."
    )
ValueError: Could not find version string in /repo/google/cloud/spanner_dbapi/version.py. File was not modified.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/app/./cli.py", line 1592, in <module>
    args.func(librarian=args.librarian, repo=args.repo, output=args.output)
    ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/./cli.py", line 1509, in handle_release_stage
    raise ValueError(f"Release stage failed: {e}") from e
ValueError: Release stage failed: Could not find version string in /repo/google/cloud/spanner_dbapi/version.py. File was not modified.

[parthea]

I was able to run librarian release stage after making this change

partheniou@partheniou-vm-3:~/git/python-spanner$ git diff
diff --git a/google/cloud/spanner_dbapi/version.py b/google/cloud/spanner_dbapi/version.py
index 6fbb80eb..0ae3005c 100644
--- a/google/cloud/spanner_dbapi/version.py
+++ b/google/cloud/spanner_dbapi/version.py
@@ -13,8 +13,8 @@
 # limitations under the License.
 
 import platform
-from google.cloud.spanner_v1 import gapic_version as package_version
 
 PY_VERSION = platform.python_version()
-VERSION = package_version.__version__
+__version__ = "3.59.0"
+VERSION = __version__
 DEFAULT_USER_AGENT = "gl-dbapi/" + VERSION