gedit XMLHelper Plugin
This plugin assists you in composing XML documents (and only XML documents, it cannot edit anything which is not a well-formed XML document). It doesn't have any clue about the structure of a document, so it is not by equal to nXML mode for Emacs or heavy weights like that, but should be sufficient to replace (now non-functional) plugin in bug 163014.
Repository for the plugin is available (you can file the issue tickets in the same place)
git clone https://gitlab.com/mcepl/gedit-xmlhelper.git
to get a local copy and copy (or symlink) xmlhelper.py, libxmlhelper.py, and xmlhelper.plugin to ~/.local/share/gedit/plugins/ and activate in Prefrences/Plugins list.
Tested with python 2.7 (hopefully should work with python 3 as well).