CI for Python 3.4 fails, because the current version of pyyaml (5.3.x) does not support Python 3.4 anymore. The change fixes the pyyaml version to 5.2 for Python 3.4.
CI for Python 3.4 fails, because the current version of pyyaml (5.3.x) does not support Python 3.4 anymore.
The change fixes the pyyaml version to 5.2 for Python 3.4.

marl/jams,marl/jams,marl/jams