po response.errorCode
▿ Optional<String>
  - some : "INVALID_CHALLENGE"

(lldb) po response.httpCode
▿ Optional<Int>
  - some : 400

(lldb) po response.isError
true

(lldb) po response.errorCode
▿ Optional<String>
  - some : "INVALID_CHALLENGE"

(lldb) po response.errorMessage
▿ Optional<String>
  - some : "User with id 2601 has already finished a challenge today"