module Jason is not available

[jay-meister]

I get this error intermittently in a test:

:gen_event handler Logger.Backends.Console installed in Logger terminating
** (exit) an exception was raised:
    ** (UndefinedFunctionError) function Jason.encode!/2 is undefined (module Jason is not available)
        (jason) Jason.encode!(%{context: %{runtime: %{application: :ev2, file: "lib/ev2/lib/sign/sign_api.ex", function: "new_envelope/3", line: 90, module_name: "Ev2.Lib.SignAPI", vm_pid: "<0.7745.0>"}, system: %{hostname: "Jacks-MacBook-Pro", pid: 96869}}, dt: "2019-09-19T14:26:34.320308Z", error: "{:error, %HTTPoison.Response{body: \"{\\\"loginAccounts\\\":[{\\\"baseUrl\\\":\\\"oh_yeah\\\"}]}\", headers: %{}, request: nil, request_url: nil, status_code: 201}}", level: :error, message: "docusign.envelope.new.request_error"}, [escape: :json])
        (timber) lib/timber/formatter.ex:73: Timber.Formatter.format/4
        (logger) lib/logger/backends/console.ex:186: Logger.Backends.Console.format_event/5
        (logger) lib/logger/backends/console.ex:140: Logger.Backends.Console.log_event/5
        (logger) lib/logger/backends/console.ex:45: Logger.Backends.Console.handle_event/2
        (stdlib) gen_event.erl:577: :gen_event.server_update/4
        (stdlib) gen_event.erl:559: :gen_event.server_notify/4
        (stdlib) gen_event.erl:300: :gen_event.handle_msg/6
        (stdlib) proc_lib.erl:249: :proc_lib.init_p_do_apply/3

It only intermittently errors once in this test for my entire testing suite.

I am currently using timber-elixir and timber-elixir-plug.

I think I can see that timber-elixir-phoenix has a configurable :json_library https://github.com/timberio/timber-elixir-phoenix/blob/master/config/config.exs#L23

But can't see that in the timber-elixir-plug https://github.com/timberio/timber-elixir-plug/blob/master/config/config.exs

The code:

      case HTTPoison.post(url, Jason.encode!(body), headers, recv_timeout: 40_000) do 
          {:ok,
           %HTTPoison.Response{
             body: res_body,
             headers: headers,
             request: %{body: req_body, headers: _req_headers},
             status_code: status_code
           }} ->
            res_body = Jason.decode!(res_body)

            Logger.error(fn ->
              {"docusign.envelope.new.failure",
               event: %{
                 response: %{
                   status_code: status_code,
                   body: res_body,
                   headers: headers,
                   request: %{body: Jason.decode!(req_body)}
                 }
               }}
            end)

            {:error, "docusign.envelope.new.failure - #{res_body["errorCode"]} (#{status_code})"}

My setup:

I've recently upgraded to Phoenix 1.4 and have removed Poison and included Jason.
mix.exs:

  defp deps do
    [
      {:phoenix, "~> 1.4.0"},
      {:plug, "~> 1.0"},
      {:plug_cowboy, "~> 2.0"},
      {:httpoison, "~> 1.0"},
      {:appsignal, "~> 1.0"},
      {:jason, "~> 1.0"},
      {:timber, "~> 3.0"},
      {:timber_plug, "~> 1.0"}
    ]
  end

config.exs

# Configure timber as logger
config :logger, :console,
  format: {Timber.Formatter, :format},
  metadata: :all

# Define json library for phoenix
config :phoenix, :json_library, Jason

test.exs

# Print only warnings and errors during test
config :logger, level: :warn