Adding custom Image attribute for category in magento 2

Question

I have tried below code for adding thumbnail image in category.

When i upload image in custom field i get below error.

Error

Attention

The file was not uploaded.

error: "The file was not uploaded." errorcode: 666

category_form.xml

<field name="thumbnail_image">
            <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">Category 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">40</item>
                    <item name="uploaderConfig" xsi:type="array">
                        <item name="url" xsi:type="url" path="catalog/category_image/upload"/>
                    </item>
                    <item name="label" xsi:type="string" translate="true">Thumbnail Image</item>
                </item>
            </argument>
        </field>

InstallData.php

$eavSetup->addAttribute('catalog_category', 'thumbnail_image', array(
    'input'   => 'image',
    'type'    => 'varchar',
    'backend' => 'catalog/category_attribute_backend_image',
    'group' => 'General',
    'label'         => 'Thumbnail Image',
    'visible'       => 1,
    'required'      => 0,
    'user_defined' => 1,
    'frontend_input' =>'',
    'global'        => \Magento\Catalog\Model\ResourceModel\Eav\Attribute::SCOPE_GLOBAL,
    'visible_on_front'  => 1,
));

di.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/Acl/etc/di.xsd">
<type name="Namespace\Module\Controller\Adminhtml\Category\Image">
    <arguments>
        <argument name="imageUploader" xsi:type="object">Magento\Catalog\CategoryImageUpload</argument>
    </arguments>
</type>
</config>