fix: downgrade pyyaml <6.0 (#2516)

Latest cython 3.0 breaks pyYAML 6.0. Installation fails with:
AttributeError: cython_sources

Cython 3.0 is in beta at the moment and this needs to be fixed upstream.

Signed-off-by: Moritz Johner <beller.moritz@googlemail.com>

hack/api-docs/Dockerfile

@@ -11,11 +11,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM alpine:3.11
+FROM alpine:3.18
 COPY requirements.txt /
 RUN apk add -U --no-cache \
     python3 \
     python3-dev \
+    py3-pip \
     musl-dev \
     git \
     openssh \

hack/api-docs/Makefile

@@ -52,8 +52,8 @@ build: image generate $(SOURCES)
 		--sig-proxy=true \
 		--rm \
 		--user $(UID):$(GID) \
-		--env GIT_COMMITTER_NAME=$(shell git config user.name) \
-		--env GIT_COMMITTER_EMAIL=$(shell git config user.email) \
+		--env "GIT_COMMITTER_NAME=$(shell git config user.name)" \
+		--env "GIT_COMMITTER_EMAIL=$(shell git config user.email)" \
 		$(MKDOCS_IMAGE) \
 		/bin/bash -c "cd /repo && $(MIKE) deploy --ignore --update-aliases -F hack/api-docs/mkdocs.yml $(DOCS_VERSION) $(DOCS_ALIAS);"
 .PHONY: build.publish

hack/api-docs/requirements.txt

@@ -12,7 +12,7 @@ mkdocs-minify-plugin==0.5.0
 pep562==1.1
 Pygments==2.15.1
 pymdown-extensions==9.11
-PyYAML==6.0
+PyYAML==5.3.1 # 6.0 is broken: https://github.com/yaml/pyyaml/issues/601
 six==1.16.0
 tornado==6.1
 mkdocs-macros-plugin==0.7.0