PyYAML fix

Change-Id: I2a15b20deb4b2c55c7db67c45a8d273b29b7600a
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/requirements.in b/requirements.in
index 89184d5..128194b 100644
--- a/requirements.in
+++ b/requirements.in
@@ -15,4 +15,4 @@
 
 pyang
 pyangbind
-pyyaml==5.3.1
\ No newline at end of file
+pyyaml>6
\ No newline at end of file