chore: use gapic-generator-python 1.0.0 (#186)

- [ ] Regenerate this pull request now.

PiperOrigin-RevId: 451250442

Source-Link: googleapis/googleapis@cca5e81

Source-Link: googleapis/googleapis-gen@0b219da
Copy-Tag: eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiMGIyMTlkYTE2MWE4YmRjYzNjNmY3YjJlZmNkODIxMDUxODJhMzBjYSJ9

Author: gcf-owl-bot[bot]

packages/google-cloud-os-login/tests/unit/gapic/oslogin_v1/test_os_login_service.py

@@ -14,7 +14,13 @@
 # limitations under the License.
 #
 import os
-import mock
+
+# try/except added for compatibility with python < 3.8
+try:
+    from unittest import mock
+    from unittest.mock import AsyncMock
+except ImportError:
+    import mock
 
 import grpc
 from grpc.experimental import aio