Remove incomplete xen support

Support for the Xen hypervisor within the charm is incomplete
and untested.  Remove Xen support and update comment to clarify
supported virt flavors.

Change-Id: I6fb87fb5eb40ad48315b563471ec4f08e7d907ce

README.md

@@ -1,8 +1,8 @@
 Overview
 ========
 
-This charm provides Nova Compute, the OpenStack compute service. It's target
-platform is Ubuntu (preferably LTS) + Openstack.
+This charm provides Nova Compute, the OpenStack compute service. Its target
+platform is Ubuntu (preferably LTS) + OpenStack.
 
 Usage
 =====

config.yaml

@@ -97,10 +97,14 @@ options:
     type: string
     default: kvm
     description: |
-      Virtualization flavor. Supported flavors are: kvm, xen, uml, lxc, qemu,
-      lxd.
-      .
-      NOTE: Changing virtualization flavor after deployment is not supported.
+      Virtualisation flavor. Supported and tested flavors are: kvm, lxd.
+
+      If using the lxd flavor, the lxd subordinate charm must also be related.
+
+      Other native libvirt flavors available to exercise (dev/test only):
+      uml, lxc, qemu.
+
+      NOTE: Changing virtualisation flavor after deployment is not supported.
   disk-cachemodes:
     type: string
     default:

hooks/nova_compute_utils.py

@@ -163,7 +163,6 @@ LATE_GIT_PACKAGES = [
     'qemu-system',
     'qemu-utils',
     'vlan',
-    'xen-system-amd64',
 ]
 
 # ubuntu packages that should not be installed when deploying from git
@@ -179,7 +178,6 @@ GIT_PACKAGE_BLACKLIST = [
     'nova-compute-lxd',
     'nova-compute-qemu',
     'nova-compute-uml',
-    'nova-compute-xen',
     'nova-network',
     'python-six',
     'quantum-plugin-openvswitch',
@@ -290,7 +288,6 @@ CEPH_RESOURCES = {
 VIRT_TYPES = {
     'kvm': ['nova-compute-kvm'],
     'qemu': ['nova-compute-qemu'],
-    'xen': ['nova-compute-xen'],
     'uml': ['nova-compute-uml'],
     'lxc': ['nova-compute-lxc'],
     'lxd': ['nova-compute-lxd'],
@@ -300,7 +297,6 @@ VIRT_TYPES = {
 LIBVIRT_URIS = {
     'kvm': 'qemu:///system',
     'qemu': 'qemu:///system',
-    'xen': 'xen:///',
     'uml': 'uml:///system',
     'lxc': 'lxc:///',
 }

unit_tests/test_nova_compute_utils.py

@@ -855,7 +855,7 @@ class NovaComputeUtilsTests(CharmTestCase):
              'dnsmasq-utils', 'ebtables', 'genisoimage', 'iptables',
              'iputils-arping', 'kpartx', 'kvm', 'netcat', 'open-iscsi',
              'parted', 'python-libvirt', 'qemu', 'qemu-system',
-             'qemu-utils', 'vlan', 'xen-system-amd64'], fatal=True)
+             'qemu-utils', 'vlan'], fatal=True)
 
     @patch('os.listdir')
     @patch('os.path.join')