minirst: fix bytes slicing defect on Python 3
This is the only lingering problem in minirst on Python
3. test-minirst.py now passes on Python 3.
Differential Revision: https://phab.mercurial-scm.org/D3478
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true