Refactor writing BUILD_META_FILE (#229)

Author: robertvolkmann

prepare.sh

@@ -27,7 +27,13 @@ fi
 echo "Generating build metadata"
 mkdir -p "${OS_FLAVOR}/context/etc/metal"
 BUILD_META_FILE="${OS_FLAVOR}/context/etc/metal/build.yaml"
-python3 -c "import yaml; from datetime import datetime; print(yaml.dump(dict(builddate=datetime.now(), commit_ref=\"${BRANCH}\", commit_sha1=\"${GITHUB_SHA}\", gitrepo=\"${GITHUB_REPOSITORY}\"), default_flow_style=False))" | tee -a "${BUILD_META_FILE}"
+python3 - <<EOF | tee -a "${BUILD_META_FILE}"
+from datetime import datetime
+print(f"builddate='{datetime.now().isoformat(' ')}'")
+print("commit_ref='${BRANCH}'")
+print("commit_sha1='${GITHUB_SHA}'")
+print("gitrepo='${GITHUB_REPOSITORY}'")
+EOF
 
 echo "remove old firecracker images"
 sudo rm -rf /var/lib/firecracker/image/* /var/lib/firecracker/kernel/*