fix(deps): pin 'google-{api,cloud}-core' to allow 2.x versions (#415)

Include comment on embargo of '>= 2.x' min versions

Per: googleapis/google-cloud-python#10566

samples/samples/conftest.py

@@ -16,6 +16,7 @@
 import time
 import uuid
 
+from google.api_core import exceptions
 from google.cloud.spanner_v1 import backup
 from google.cloud.spanner_v1 import client
 from google.cloud.spanner_v1 import database
@@ -90,7 +91,8 @@ def sample_instance(
             "created": str(int(time.time()))
         },
     )
-    op = sample_instance.create()
+    retry_429 = retry.RetryErrors(exceptions.ResourceExhausted, delay=15)
+    op = retry_429(sample_instance.create)()
     op.result(120)  # block until completion
 
     # Eventual consistency check

setup.py

@@ -29,8 +29,14 @@
 # 'Development Status :: 5 - Production/Stable'
 release_status = "Development Status :: 5 - Production/Stable"
 dependencies = [
-    "google-api-core[grpc] >= 1.26.0, <2.0.0dev",
-    "google-cloud-core >= 1.4.1, < 2.0dev",
+    # NOTE: Maintainers, please do not require google-api-core>=2.x.x
+    # Until this issue is closed
+    # https://github.com/googleapis/google-cloud-python/issues/10566
+    "google-api-core[grpc] >= 1.26.0, <3.0.0dev",
+    # NOTE: Maintainers, please do not require google-cloud-core>=2.x.x
+    # Until this issue is closed
+    # https://github.com/googleapis/google-cloud-python/issues/10566
+    "google-cloud-core >= 1.4.1, < 3.0dev",
     "grpc-google-iam-v1 >= 0.12.3, < 0.13dev",
     "proto-plus >= 1.11.0",
     "sqlparse >= 0.3.0",