Failed on wercker-labs/docker

[spesnova]

This step failed on wercker-labs/docker.
Because of no ruby runtime in the box.

cd $WERCKER_SOURCE_DIR
$ export WERCKER_STEP_ROOT="/wercker/steps/wantedly/pretty-slack-notify/0.2.2"
$ export WERCKER_STEP_ID="0bf5c28c-d420-4076-8299-4888cc08fe7d"
$ export WERCKER_STEP_NAME="pretty-slack-notify"
$ export WERCKER_REPORT_NUMBERS_FILE="$WERCKER_REPORT_DIR/$WERCKER_STEP_ID/numbers.ini"
$ export WERCKER_REPORT_MESSAGE_FILE="$WERCKER_REPORT_DIR/$WERCKER_STEP_ID/message.txt"
$ export WERCKER_REPORT_ARTIFACTS_DIR="$WERCKER_REPORT_DIR/$WERCKER_STEP_ID/artifacts"
$ mkdir -p $WERCKER_REPORT_ARTIFACTS_DIR
$ export WERCKER_STEP_TEMP="/tmp/$WERCKER_STEP_ID"
$ source '/wercker/wercker-build-essentials/init.sh'
$ mkdir -p $WERCKER_STEP_TEMP
$ export WERCKER_PRETTY_SLACK_NOTIFY_WEBHOOK_URL="$SLACK_WEBHOOK_URL"
$ export WERCKER_PRETTY_SLACK_NOTIFY_CHANNEL="$SLACK_CHANNEL"
$ source "$WERCKER_STEP_ROOT/run.sh"
-bash: [: =: unary operator expected
You need to use a box that installed ruby.
/usr/bin/env: ruby: No such file or directory

https://app.wercker.com/#buildstep/548ec1432ca6bc21553df01d

[spesnova]

got no such file or directory

[spesnova]

fixed