Fix conflicts with pyyaml version

Author: epou

requirements/common.pip

@@ -83,7 +83,6 @@ python-dateutil==2.8.1
 python-geohash==0.8.5
 python-slugify==4.0.1
 python3-memcached==1.51
-PyYAML==5.1.2
 redgreenunittest==0.1.1
 redis==2.10.3
 requests==2.18.1