Fails when importing __future__ as renaming it

[horta]

Operating system: Darwin horta-ml 17.6.0 Darwin Kernel Version 17.6.0
Python version: Python 3.6.6 :: Anaconda custom (64-bit)
Black version: 18.6b4
Does also happen on master: yes

This works:

# test1.py
from __future__ import absolute_import

This does not work:

# test2.py
from __future__ import absolute_import as _absolute_import

Output:

error: cannot format test2.py:
All done! 💥 💔 💥
1 file failed to reformat.

[zsol]

Looks like this is a bug in how black processes future imports. Thanks for reporting, will fix!