没有将 Symbol 隐式转换为 String？在 rails 应用中 在 rspec 测试用例中

no implicit conversion of Symbol into String? in rails application in rspec testcase 

  #typhoeus running the request
  Typhoeus::Request.new("#{BASE_URI}",
  method: :post,
  body: lead,
  headers: { Accept: "application/json" },
  verbose: true,
  ssl_verifypeer: false).run

当我删除 headers 行然后调用 Http 请求时 运行 请求的测试用例 运行 时，斑疹伤寒抛出上述错误 

Typhoeus::Request.new("#{BASE_URI}",
{
  method: :post,
  body: lead,
  headers: { Accept: "application/json" },
  verbose: true,
  ssl_verifypeer: false
}).run

问题是 (Accept: "application/json") 而我改为 ('Accept' => "application/json") 效果很好。