Fix bugs in doc generation

requirements.txt

 git+https://haufs:s--zGku2dzxtv6so2xsu@git.xfel.eu/gitlab/detectors/nbparameterise.git
 git+https://haufs:s--zGku2dzxtv6so2xsu@git.xfel.eu/gitlab/detectors/cal_db_interactive.git
-pypandoc
+pypandoc<2.0.0
 nbconvert
 astcheck
 astsearch
@@ -9,5 +9,6 @@ tabulate
 h5py
 unittest-xml-reporting
 zmq
+lxml
 ./cal_tools
 .