XmlValTran
Gedit Plugin for XML Validation and Transformation
...To install:
1) Download the xmlvaltran.py and xmlvaltran.plugin files to the "~/.local/share/gedit/plugins/" directory. If the directory does not exist, create it: "mkdir -p ~/.local/share/gedit/plugins/"
2) Start or restart Gedit, and go to "Edit -> Preferences -> Plugins".
3) Select the checkbox next to "XML Validator/Transformer". The plugin will be displayed in the side panel of Gedit.