Module Warning (from ./node_modules/vue-loader/lib/loaders/templateLoader.js):
(Emitted value instead of an instance of Error) the "scope" attribute for scoped slots have been deprecated and replaced by "slot-scope" since 2.5. The new "slot-scope" attribute can also be used on plain elements in addition to to denote scoped slots.
What is wrong with that(?):
<template slot="item" slot-scope="prop">
<configuration-form v-model="prop.item" @input="isValid"></configuration-form>
</template>