repos:
-   repo: git://github.com/pre-commit/pre-commit-hooks
    rev: v2.2.3
    hooks:
    -   id: trailing-whitespace
        args: [--markdown-linebreak-ext=md,markdown]

(spice) → pre-commit run --verbose trailing-whitespace
[trailing-whitespace] Trim Trailing Whitespace...........................Failed
hookid: trailing-whitespace

Traceback (most recent call last):
  File "/Users/eedwards/.cache/pre-commit/reporo4_9zb8/py_env-python3.6/bin/trailing-whitespace-fixer", line 11, in <module>
    sys.exit(main())
  File "/Users/eedwards/.cache/pre-commit/reporo4_9zb8/py_env-python3.6/lib/python3.6/site-packages/pre_commit_hooks/trailing_whitespace_fixer.py", line 81, in main
    if _fix_file(filename, md):
  File "/Users/eedwards/.cache/pre-commit/reporo4_9zb8/py_env-python3.6/lib/python3.6/site-packages/pre_commit_hooks/trailing_whitespace_fixer.py", line 11, in _fix_file
    with open(filename, mode='rb') as file_processed:
FileNotFoundError: [Errno 2] No such file or directory: 'markdown'