add lxml dependency

README.md

@@ -40,6 +40,8 @@ install it by running `pip install -U mako` on a Python-enabled command prompt
 4. If you are not using WinPython, you also need to install the Jinja2
 templating engine by running `pip install -U jinja2` on a Python-enabled command
 prompt
+5. If you want to use the XML loader you need to install the lxml package: 
+`pip install -U lxml`.
 
 You can check these dependencies by running the script
 `tools/dependency_check.py` if you already have a python interpreter installed.

tools/dependency_check.py

@@ -64,4 +64,13 @@ def done(status=0):
     l.append('- GUI will not run, please install PyQt5 and retry!')
 lb.append(l)
 
+# Checking lxml
+l = ['Checking lxml... ']
+try:
+    from lxml import etree, objectify
+    l.append('Ok!')
+except BaseException:
+    l.append('- XML loader will not run, you should install lxml and retry!')
+lb.append(l)
+
 done(0)