Use library to generate XML in maketests instead of system() #906
Oddly, there were two
Oddly, there were two `gen_xml` methods. The one being used was shelling out to `latexml`. This doesn't work when working with a development environment where `latexml` isn't on the path. The other `gen_xml` method uses the library, which works with local development environments. A nice side-effect is this is the same approach used by `make test`, which seems more resilient somehow.