text: Title: [bug] list command must error for not found key
  Body: ```bash
  # /venv/bin/dynaconf list -k "D" --json
  Key not found
  # echo $?
  0
  ```
  
  Expected: `1` retcode
  
  ---
  
  Open for discussion:
  
  - Should retcode be `1`
  - Should return empty json `{}`
  
  ?