PyYAML bug workaround

Change-Id: I8daf085130415d248e0e209bf18af1243a37cd1e
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/requirements.in b/requirements.in
index aa36ac5..8b87683 100644
--- a/requirements.in
+++ b/requirements.in
@@ -16,7 +16,7 @@
 pymongo
 aiokafka
 charset-normalizer<4 # Required by aiohttp in LCM
-pyyaml==5.4.1
+pyyaml==5.3.1
 pycryptodome
 dataclasses
 motor