element show-overflow-tooltip 无效
    解决方案：

    1. <el-table-column show-overflow-tooltip prop="policeTypeName" label="警员类型" align="center">
    2.   <template slot-scope="{row}">
    3.     <span>{{row.policeTypeName}}</span>
    4.   </template>
    5. </el-table-column>

    并设置

    1. >>>.cell
    2.   display inline-block