CI: fix xml tests on RHEL 8 (#7827)

* Try to fix xml installation on RHEL.

* Install python-lxml on RHEL 8. Should speed up tests considerably.

tests/integration/targets/xml/tasks/main.yml

@@ -14,6 +14,15 @@
     state: present
   when: ansible_os_family == "FreeBSD"
 
+- name: Install requirements (RHEL 8)
+  package:
+    name:
+      - libxml2-devel
+      - libxslt-devel
+      - python3-lxml
+    state: present
+  when: ansible_distribution == "RedHat" and ansible_distribution_major_version == "8"
+
 # Needed for MacOSX !
 - name: Install lxml
   pip: