ci: fix publish workflow by adding missing dependency

Author: consideRatio

.github/workflows/publish.yml

@@ -36,7 +36,7 @@ jobs:
           #        Upstream issue:  https://github.com/docker/docker-py/issues/2807
           #        Breaking commit: https://github.com/docker/docker-py/commit/c8fba210a222d4f7fde90da8f48db1e7faa637ec
           #
-          pip install --no-cache-dir chartpress==1.0.* six
+          pip install --no-cache-dir chartpress==1.0.* six pyyaml
 
       - name: Setup push rights to jupyterhub/helm-chart
         # This was setup by...

dev-requirements.txt

@@ -8,6 +8,10 @@ jupyterhub
 pytest
 pytest-asyncio
 pytest-cov
+# pyyaml is used by the scripts in tools/ and could absolutely be replaced by
+# using ruamel.yaml. ruamel.yaml is more powerful than pyyaml, and that is
+# relevant when writing YAML files back after having loaded them from disk.
+pyyaml
 requests
 ruamel.yaml>=0.15
 # FIXME: six is required by docker 5.0.0 but isn't explicitly required any more.