message: Fix MAC BUILD.bazel file.
diff: @@ -25,8 +25,8 @@ py_library(
  )
  py_library(
  - name = "mac_key_manager",
  - srcs = ["mac_key_manager.py"],
  + name = "_mac_key_manager",
  + srcs = ["_mac_key_manager.py"],
  srcs_version = "PY3",
  deps = [
  ":_mac",
  @@ -38,8 +38,8 @@ py_library(
  )
  py_test(
  - name = "mac_key_manager_test",
  - srcs = ["mac_key_manager_test.py"],
  + name = "_mac_key_manager_test",
  + srcs = ["_mac_key_manager_test.py"],
  srcs_version = "PY3",
  deps = [
  ":mac",
  @@ -65,8 +65,8 @@ py_library(
  )
  py_test(
  - name = "mac_wrapper_test",
  - srcs = ["mac_wrapper_test.py"],
  + name = "_mac_wrapper_test",
  + srcs = ["_mac_wrapper_test.py"],
  srcs_version = "PY3",
  deps = [
  ":mac",
  @@ -89,8 +89,8 @@ py_library(
  )
  py_test(
  - name = "mac_key_templates_test",
  - srcs = ["mac_key_templates_test.py"],
  + name = "_mac_key_templates_test",
  + srcs = ["_mac_key_templates_test.py"],
  deps = [
  ":mac",
  requirement("absl-py"),
  