Modernize cancellation example

examples/python/cancellation/BUILD.bazel

@@ -15,7 +15,7 @@
 # limitations under the License.
 
 load("@grpc_python_dependencies//:requirements.bzl", "requirement")
-load("//bazel:python_rules.bzl", "py_proto_library")
+load("//bazel:python_rules.bzl", "py_proto_library", "py_grpc_library")
 
 package(default_testonly = 1)
 
@@ -25,9 +25,14 @@ proto_library(
 )
 
 py_proto_library(
-    name = "hash_name_proto_pb2",
+    name = "hash_name_py_pb2",
-    deps = [":hash_name_proto"],
+    srcs = [":hash_name_proto"],
-    well_known_protos = False,
+)
+
+py_grpc_library(
+    name = "hash_name_py_pb2_grpc",
+    srcs = [":hash_name_proto"],
+    deps = [":hash_name_py_pb2"],
 )
 
 py_binary(
@@ -35,8 +40,9 @@ py_binary(
     srcs = ["client.py"],
     deps = [
         "//src/python/grpcio/grpc:grpcio",
-        ":hash_name_proto_pb2",
+        ":hash_name_py_pb2",
-        requirement("six"),
+        ":hash_name_py_pb2_grpc",
+        "//external:six"
     ],
     srcs_version = "PY2AND3",
 )
@@ -46,7 +52,7 @@ py_library(
     srcs = ["search.py"],
     srcs_version = "PY2AND3",
     deps = [
-        ":hash_name_proto_pb2",
+        ":hash_name_py_pb2",
     ],
 )
 
@@ -55,10 +61,10 @@ py_binary(
     srcs = ["server.py"],
     deps = [
         "//src/python/grpcio/grpc:grpcio",
-        ":hash_name_proto_pb2",
+        ":hash_name_py_pb2",
         ":search",
     ] + select({
-        "//conditions:default": [requirement("futures")],
+        "//conditions:default": ["@futures//:futures"],
         "//:python3": [],
     }),
     srcs_version = "PY2AND3",