def check_headers(headers):
    assert isinstance(headers,list), (
        "Headers (%r) must be of type list: %r"
        % (headers, type(headers)))
    header_names = {}
    for item in headers:
        assert isinstance(item, tuple), (
            "Individual headers (%r) must be of type tuple: %r"
            % (item, type(item)))
        assert len(item) == 2
        name, value = item
        assert name.lower() != 'status', (
            "The Status header cannot be used; it conflicts with CGI "
            "script, and HTTP status is not given through headers "
            "(value: %r)." % value)
        header_names[name.lower()] = None
        assert '\n' not in name and ':' not in name, (
            name % "Header names may not contain ':' or '\\n': %r")
        assert header_re.search(name), "Bad header name: %r" % name
        assert not name.endswith('-') and not name.endswith('_'), (
            "Names may not end in '-' or '_': %r" % name)
        assert not bad_header_value_re.search(value), (
            "Bad header value: %r (bad char: %r)"
            % (value, bad_header_value_re.search(value).group(0)))
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Paste-2.0.1/paste/lint.py/check_headers/swapped operands of `%`