Cannot create a etc/view.xml file with an images tag with an attribute module other than Magento_Catalog

[tzyganu]

Description
I've been trying to create an extension with an entity that has an image attribute. I want to show on frontend the resized image similar to how the product image is resized in the product list page.
For this I've created image model and helper and the builder block.
The resize works perfectly if I specify the width and height (and other attributes) in the template file when calling $block->getImage(....).
But I wanted to do it properly and read the resize values from the view.xml file
Then I created a file called etc/view.xml and every page crashes

Steps to reproduce

Create a file called etc/view.xml in any module with this content

<view xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Config/etc/view.xsd">
    <media>
        <images module="Namespace_Module"><!-- the module attribute can be anything other than Magento_Catalog -->
            <image id="whatever_here">
                <width>60</width>
                <height>60</height>
            </image>
        </images>
    </media>
</view>

Expected result

I should be able to read my values using Magento\Framework\View\ConfigInterface::getViewConfig()::getMediaAttributes('Namespace_Module', 'image', 'whatever_here')

Actual result
Every page crashes because the merged view.xml files apparently are not valid.
The error message is

Exception #0 (Magento\Framework\Exception\LocalizedException): Invalid Document
Element 'images': This element is not expected.
Line: 22

Line 22 in my file is <images module="Namespace_Module">

Additional info:
Changing Namespace_Module to Magento_Catalog makes the error go away, but then again I cannot have a configuration for my module.

[nicolaspernot]

Same problem here. I will try to find time for propose a pull request in (near?) future.
Problem comes from the Config/etc/view.xsd.

Just change this part:

<xs:complexType name="mediaType" mixed="true">
        <xs:all>
            <xs:element name="images" type="imageType" minOccurs="0"/>
            <xs:element name="videos" type="videoType" minOccurs="0"/>
        </xs:all>
    </xs:complexType>

by:

<xs:complexType name="mediaType" mixed="true">
        <xs:sequence>
            <xs:element name="images" type="imageType" minOccurs="0" maxOccurs="unbounded" />
            <xs:element name="videos" type="videoType" minOccurs="0" maxOccurs="unbounded" />
        </xs:sequence>
    </xs:complexType>

And that seems solve the problems.

[adragus-inviqa]

Confirmed. Can someone get the ball rolling on this one, please? Mark it up for grabs or something, for visibility.

[SiarheyUchukhlebau]

Any news about when this bug can be fixed?

[tzyganu]

I see that the PR for this was accepted. Can I close the issue?

[magento-team]

Internal ticket to track issue progress: MAGETWO-70256

[magento-engcom-team]

@tzyganu @ajpevers thank you for your report.
The fix for this issue is already available in release 2.2.0