message: Define ipynb in build file
diff: @@ -8,6 +8,12 @@ licenses(["notice"]) # Apache 2.0
  package(default_visibility = ["//tensorflow:internal"])
  +py_library(
  + name = "ipynb",
  + srcs = ["ipynb.py"],
  + srcs_version = "PY2AND3",
  +)
  +
  py_library(
  name = "ast_edits",
  srcs = ["ast_edits.py"],
  @@ -87,6 +93,7 @@ py_binary(
  srcs_version = "PY2AND3",
  deps = [
  ":ast_edits",
  + ":ipynb",
  ":tf_upgrade_v2_lib",
  ],
  )
  