Unknown token "lightning.utilitySprite" default value was used instead.
Failed to load resource: the server responded with a status of 404 (Not Found)
https://(mydomainname)--(sandboxname).lightning.force.com/assets/icons/utility-sprite/svg/symbols.svg#chevronleft

<aura:application >
    <ltng:require styles="{!$Resource.SLDS213 + '/assets/styles/salesforce-lightning-design-system-ltng.min.css'}"/>

    <div class="(scoped_name)-slds">
        <c:testDynamicTabset_Parent />
    </div>
</aura:application>

<aura:component >
    <lightning:tabset aura:id="dynamicTabset">
        <lightning:tab aura:id="tab1" label="Tab 1">Tab 1 Body</lightning:tab>
        <lightning:tab aura:id="tab2" label="Tab 2">Tab 2 Body</lightning:tab>
        <lightning:tab aura:id="tab3" label="Tab 3">Tab 3 Body</lightning:tab>
        (omitted middle lines)
        <lightning:tab aura:id="tab3" label="Tab 18">Tab 18 Body</lightning:tab>
        <lightning:tab aura:id="tab3" label="Tab 19">Tab 19 Body</lightning:tab>
        <lightning:tab aura:id="tab3" label="Tab 20">Tab 20 Body</lightning:tab>
    </lightning:tabset>

</aura:component>