message: Make CERTIFICATE_NAME readonly
diff: # Make a certificate for development purposes, and populate the
  # corresponding environment variables.
  -CERTIFICATE_NAME="$1/shadowbox-selfsigned-dev"
  +readonly CERTIFICATE_NAME="$1/shadowbox-selfsigned-dev"
  export SB_CERTIFICATE_FILE="${CERTIFICATE_NAME}.crt"
  export SB_PRIVATE_KEY_FILE="${CERTIFICATE_NAME}.key"
  declare -a openssl_req_flags=(
  