PyYAML bug workaround

Change-Id: I75f9a7dbc9e5982b97f1dcecdcd28ed74f42f473
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/requirements.txt b/requirements.txt
index fe00489..6d20138 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -267,7 +267,7 @@
     # via tzlocal
 pyvcloud==23.0.4
     # via -r requirements.in
-pyyaml==5.4.1
+pyyaml==5.3.1
     # via
     #   -r requirements.in
     #   cliff