Validate Gramps XML

[bartfeenstra]

Validate Gramps XML using the official Doctype. We can download it with the Fetch API. Make sure we fix the major version if we can! Can we pre build the DTD?

The lxml stdlib lets us validate XML against DTD

[romjerome]

I do not know if this could help, but I tested some Gramps XML validations in the past (XSD, DTD, RNG). Here, the related sections : https://github.com/gramps-project/addons-source/blob/master/lxml/lxmlGramplet.py#L291