Request to print line as well along with file name to identify the line which is failing

[dvsanthosh]

pre-commit-hooks/pre_commit_hooks/detect_private_key.py

Line 31 in e5e94e8

private_key_files.append(filename)

Here only file name is printed but not the line without which it will be very difficult to identify which line is failing especially in large files. Pls add line as well.

[asottile]

patches welcome