def nova_one_import_per_line(logical_line):
    """
    nova HACKING guide recommends one import per line:
    Do not import more than one module per line

    Examples:
    BAD: from nova.rpc.common import RemoteError, LOG
    BAD: from sqlalchemy import MetaData, Table
    N301
    """
    pos = logical_line.find(',')
    if (pos > -1 and (logical_line.startswith("import ") or
       (logical_line.startswith("from ") and
       logical_line.split()[2] == "import"))):
        return pos, "NOVA N301: one import per line"