use openssl instead of python to generate eks cluster names

because python is not part of Amazon's container image anymore

dockerfiles/eks-deployer/Dockerfile

@@ -6,7 +6,7 @@
 FROM weaveworks/eksctl:v0.212.0 AS eksctl
 FROM mikefarah/yq:4.47.1 AS yq
 FROM amazon/aws-cli:2.27.62
-RUN yum update -y && yum install -y jq && yum install -y perl-Digest-SHA && yum clean all
+RUN yum update -y && yum install -y jq perl-Digest-SHA openssl && yum clean all
 COPY --from=eksctl eksctl /usr/local/bin/eksctl
 COPY --from=yq /usr/bin/yq /usr/local/bin/yq
 

pipelines/shared-tasks/deploy-eks-cluster/task.sh

@@ -13,7 +13,7 @@ aws configure set credential_source Environment --profile service-account
 aws configure set role_arn "$AWS_ROLE_ARN" --profile service-account
 
 # Set some variables.
-CLUSTER_NAME="eks-$(python -c 'import os,binascii; print binascii.b2a_hex(os.urandom(8))')"
+CLUSTER_NAME="eks-$(openssl rand -hex 8)"
 ADMIN_USERNAME="$CLUSTER_NAME-admin"
 export CLUSTER_NAME
 export ADMIN_USERNAME