standard_library.install_aliases() doesn't publish tkinter.simpledialog.askstring in 2.7

[nat-goodspeed]

$ python
Python 2.7.15 (default, Oct  1 2018, 15:59:56) 
[GCC 4.2.1 Compatible Apple LLVM 10.0.0 (clang-1000.11.45.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from future import standard_library
>>> standard_library.install_aliases()
>>> from tkinter.simpledialog import askstring
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name askstring

This reproduces with both future 0.16.0 and 0.17.1.