Bump PyYaml to 5.3.1 and replace pycrypto 2.6.1 with pycryptodome 3.9.8 (#379)

Author: glukhman

.circleci/config.yml

@@ -220,7 +220,7 @@ commands:
           command: virtualenv env
       - run:
           name: install tox
-          command: pip install --user pygithub pyyaml>=5.3.1,<5.4
+          command: pip install --user pygithub pyyaml==5.3.1
       - run:
           name: upgrade setuptools
           command: pip install --upgrade setuptools