how can create category attribute thumbnail in magento 2.1

[khamarpratik]

i create category attribute thumbnail using install data

i create require file as per new magento 2.1 This is my category_form.xml

<?xml version="1.0" encoding="UTF-8"?>
<form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
    <fieldset name="content">
        <field name="thumbnail">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="dataType" xsi:type="string">string</item>
                    <item name="source" xsi:type="string">category</item>
                    <item name="label" xsi:type="string" translate="true">Thumbnail Image</item>
                    <item name="visible" xsi:type="boolean">true</item>
                    <item name="formElement" xsi:type="string">fileUploader</item>
                    <item name="elementTmpl" xsi:type="string">ui/form/element/uploader/uploader</item>
                    <item name="previewTmpl" xsi:type="string">Magento_Catalog/image-preview</item>
                    <item name="required" xsi:type="boolean">false</item>
                    <item name="sortOrder" xsi:type="number">30</item>
                    <item name="uploaderConfig" xsi:type="array">
                        <item name="url" xsi:type="url" path="catalog/category_image/upload"/>
                    </item>
                </item>
            </argument>
        </field>
    </fieldset>
</form>

when i upload image i show following error

{error: "The file was not uploaded.", errorcode: 666}
error: "The file was not uploaded."
errorcode: 666