Push Python 3 docker images to *-py3

.ci/build-docker.sh

@@ -18,7 +18,6 @@ set -ex
 # We speed up the build process by copying built artifacts from ARTIFACT_BASE
 # during docker build. See /docker/Dockerfile for more details.
 ARTIFACT_BASE=${ARTIFACT_BASE:-sagemath/sagemath-dev:develop}
-WITH_PYTHON=${WITH_PYTHON:-2}
 
 # Seed our cache with $ARTIFACT_BASE if it exists.
 docker pull "$ARTIFACT_BASE" > /dev/null || true

.ci/update-env.sh

@@ -27,6 +27,8 @@ if [ -n "$CI_MONKEY_PATCH" ]; then
     $SCRIPT
 fi
 
+WITH_PYTHON=${WITH_PYTHON:-2}
+
 # From the docker documentation: "A tag name must be valid ASCII and may
 # contain lowercase and uppercase letters, digits, underscores, periods and
 # dashes. A tag name may not start with a period or a dash and may contain a
@@ -36,6 +38,10 @@ export DOCKER_TAG=`echo $DOCKER_TAG | tr -d '[:space:]' | tr -c '[:alnum:]_.-' '
 [[ -z "$DOCKER_TAG" ]] && export DOCKER_TAG=none
 [[ "$DOCKER_TAG" = "master" ]] && export DOCKER_TAG=latest
 
+if [ $WITH_PYTHON = 3 ]; then
+    export DOCKER_TAG=$DOCKER_TAG-py3
+fi
+
 export DOCKER_IMAGE_CLI=${DOCKER_NAMESPACE:-sagemath}/sagemath:$DOCKER_TAG
 export DOCKER_IMAGE_DEV=${DOCKER_NAMESPACE:-sagemath}/sagemath-dev:$DOCKER_TAG
 

.gitlab-ci.yml

@@ -184,7 +184,7 @@ push-dockerhub-dev:
 .py3:
   variables:
     WITH_PYTHON: 3
-    DOCKER_TAG_SUFFIX: "-py3"
+    DEFAULT_ARTIFACT_BASE: sagemath/sagemath-dev:develop-py3
 
 build-from-latest-py3:
   extends: