import.xml doesn't allow numbers in vendor name and class name

[tzsolti]

Preconditions

1. Magento 2.

Steps to reproduce

1. Create a simple module with a vendor name which contains at least one number (ex. test123) which creates an import entity
2. etc/import.xml will look something like:

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_ImportExport:etc/import.xsd">
<entity name="catalog_product" label="Products test" model="test123\somename\Model\Something" behaviorModel="Magento\ImportExport\Model\Source\Import\Behavior\Basic" />
</config>

3. Enable module, clear the cache and open the Magento backend Import page

Expected result

1. It should load the import page

Actual result

1. The site will die with an error message similar to this:

Invalid XML in file <path_to_website_root>/app/code/test123/somename/etc/import.xml:
Element 'entity', attribute 'model': [facet 'pattern'] The value 'test123\somename\Model\Something' is not accepted by the pattern '[A-Za-z_\]+'.
Line: 3

Element 'entity', attribute 'model': 'test123\somename\Model\Something' is not a valid value of the atomic type 'modelName'.
Line: 3

The same happens also for export.xml.

[maksek]

@tzsolti, thanks for reporting, we are aware of the issue, and going to resolve it.

[nhp]

Would be fixed by PR #5420