replaced by catching a KeyError exception.
*   `tf.contrib.data`
    *   Deprecate, and replace by tf.data.experimental.
*   Other:
    *   Instead of jemalloc, revert back to using system malloc since it
        simplifies build and has comparable performance.
    *   Remove integer types from `tf.nn.softplus` and `tf.nn.softsign` OpDefs.