Describe the bug

Slicing of bracketed expressions is broken by too eager removal of the brackets.

To Reproduce

1. Try to reformat a file containing return ('%x' % value)[-12:]
2. The resulting expression is not producing equivalent result: return '%x' % mac[-12:]

Expected behavior

Expected to not remove the brackets in this case.

Environment (please complete the following information):

• Version: master
• OS and Python version: Linux, Python 3.7.4

Does this bug also happen on master? To answer this, you have two options:

Yes.