PyYAML fix

Change-Id: Ib818df660f2f1e4be1c1caf9e1626362dfbda9d6
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/requirements.in b/requirements.in
index abddaa5..1dd93f6 100644
--- a/requirements.in
+++ b/requirements.in
@@ -34,6 +34,6 @@
 python-novaclient
 python-cinderclient==8.3.0
 pyvcloud
-pyyaml==5.3.1
+pyyaml>6
 requests
 six