def check_embed_envvar(param)
      return unless param =~ /<%=\s*ENV\[[\'\"]?(.+)[\'\"]\]?\s*%>/
      envvar_name = Regexp.last_match(1)
      if !ENV.key?(envvar_name)
        @logger.error "Variable name: #{envvar_name} is not found in ENV"
      elsif ENV[envvar_name] =~ /^\s*$/
        @logger.warn "Env var: #{envvar_name} exists, but null string"
      end
    end
def check_embed_envvar(param)
      return unless param =~ /<%=\s*ENV\[[\'\"]?(.+)[\'\"]\]?\s*%>/
      envvar_name = Regexp.last_match(1)
      if !ENV.key?(envvar_name)
        @logger.error "Variable name: #{envvar_name} is not found in ENV"
      elsif ENV[envvar_name] =~ /^\s*$/
        @logger.warn "Env var: #{envvar_name} exists, but null string"
      end
    end
Error checking of environment variable to embed
 @param param [String] Embedding target command