Return text of unified diff between original and fixed.

def get_diff(original, fixed, file_name,
             original_label='original', fixed_label='fixed'):
    """Return text of unified diff between original and fixed."""
    original, fixed = original.splitlines(True), fixed.splitlines(True)
    newline = '\n'

    from difflib import unified_diff
    diff = unified_diff(original, fixed,
                        os.path.join(original_label, file_name),
                        os.path.join(fixed_label, file_name),
                        lineterm=newline)
    text = ''
    for line in diff:
        text += line
        # Work around missing newline (http://bugs.python.org/issue2142).
        if not line.endswith(newline):
            text += newline + r'\ No newline at end of file' + newline
    return text