text: Title: [bug] Error handling on dynaconf get CLI 
  Body: **Describe the bug**
  When using get to read a non existent variable it outputs the python traceback to the CLI
  
  **To Reproduce**
  ```console
  $ dynaconf get DONTEXIST
  Traceback (most recent call last):
    File "/venv/bin/dynaconf", line 8, in <module>
      sys.exit(main())
    File "/src/dynaconf/dynaconf/vendor/click/core.py", line 857, in __call__
      return self.main(*args, **kwargs)
    File "/src/dynaconf/dynaconf/vendor/click/core.py", line 810, in main
      rv = self.invoke(ctx)
    File "/src/dynaconf/dynaconf/vendor/click/core.py", line 1292, in invoke
      return _process_result(sub_ctx.command.invoke(sub_ctx))
    File "/src/dynaconf/dynaconf/vendor/click/core.py", line 1099, in invoke
      return ctx.invoke(self.callback, **ctx.params)
    File "/src/dynaconf/dynaconf/vendor/click/core.py", line 613, in invoke
      return callback(*args, **kwargs)
    File "/src/dynaconf/dynaconf/cli.py", line 476, in get
      result = settings[key]  # let the keyerror raises
    File "/src/dynaconf/dynaconf/utils/functional.py", line 19, in inner
      return func(self._wrapped, *args)
    File "/src/dynaconf/dynaconf/base.py", line 315, in __getitem__
      raise KeyError(f"{item} does not exist")
  KeyError: 'DONTEXIST does not exist'
  ```
  
  **Expected behavior**
  
  ```console
  $ dynaconf get DONTEXIST
  Key not found.  # stderr
  $ echo $?   # proper retcode
  1
  ```
  
  The same behavior as we have in `list`
  
  ```console
  $ dynaconf list -k DONTEXIST
  Django app detected
  Working in development environment 
  Key not found
  ```
  