[Libguestfs] [PATCH nbdkit] plugins: python: Fix imageio example instructions

[Nir Soffer]

Fix the instructions so they should work now on CentOS 8.2:
- Add note about oVirt setup
- List all required packages
- Add missing -W flag to the qemu-img command

I tested this on Fedora 32, with ovirt-engine-sdk built from source,
since the package is not available on Fedora 31 or 32, and the Fedora
30 package cannot be installed on Fedora 32.

Signed-off-by: Nir Soffer <nsoffer at redhat.com>
---
 plugins/python/examples/imageio.py | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/plugins/python/examples/imageio.py b/plugins/python/examples/imageio.py
index f8ade7a2..38ad5ac4 100644
--- a/plugins/python/examples/imageio.py
+++ b/plugins/python/examples/imageio.py
@@ -4,10 +4,18 @@
 #
 # Upload and download images to oVirt with nbdkit and qemu-img.
 #
-# Install ovirt-imageio-client
+# This assumes you have an oVirt environment. If you don't please see
+# https://ovirt.org/ for info on how to install oVirt.
 #
-#   dnf copr enable nsoffer/ovirt-imageio-preview
-#   dnf install ovirt-imageio-client
+# Install ovirt-release package:
+#
+#   dnf install http://resources.ovirt.org/pub/yum-repo/ovirt-release-master.rpm
+#
+# Install required packages:
+#
+#   dnf install ovirt-imageio-client python3-ovirt-engine-sdk4
+#
+# Note: python3-ovirt-engine-sdk4 is not available yet for Fedora 31 and 32.
 #
 # To upload or download images, you need to start an image transfer. The
 # easiest way is using oVirt image_transfer.py example:
@@ -33,7 +41,7 @@
 #
 # To upload an image run:
 #
-#   qemu-img convert -n -f raw -O raw disk.img \
+#   qemu-img convert -n -f raw -O raw -W disk.img \
 #       nbd+unix:///\?socket=/tmp/nbd.sock
 #
 # Downloading image is not efficient with this version, since we don't report
-- 
2.26.2