client/securedrop_client/resources/css/checker_tooltip.css

QPushButton#Checker{
    border: none;
    margin-right: 8px;
}

#Checker QToolTip{
    font-family: Source Sans Pro;
    font-style: normal;
    font-size: 12px;
    border: none;
    padding: 2px;
    background-color: #ffffff;
}