text: Title: [DO] Unexpect output in `sky check`
  Body: <!-- Describe the bug report / feature request here -->
  
  `sky check` shows a long output when DO dependencies are not setup. We should avoid the long error message, and make it more user friendly, e.g. see other clouds below
  ```
   DO: disabled                              
      Reason: Traceback (most recent call last):
    File "/workspaces/skypilot/sky/clouds/do.py", line 263, in check_credentials
      do_utils.client().droplets.list()
    File "/workspaces/skypilot/sky/provision/do/utils.py", line 94, in client
      _client = _init_client()
    File "/workspaces/skypilot/sky/provision/do/utils.py", line 56, in _init_client
      raise DigitalOceanError(
  sky.provision.do.utils.DigitalOceanError: no credentials file found from the following paths ['/home/vscode/Library/Application Support/doctl/config.yaml', '/home/vscode/.config/doctl/config.yaml']
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File "/workspaces/skypilot/sky/adaptors/common.py", line 31, in load_module
      self._module = importlib.import_module(self._module_name)
    File "/opt/conda/envs/sky/lib/python3.10/importlib/__init__.py", line 126, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
    File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
    File "<frozen importlib._bootstrap>", line 1004, in _find_and_load_unlocked
  ModuleNotFoundError: No module named 'pydo'
  
  The above exception was the direct cause of the following exception:
  
  Traceback (most recent call last):
    File "/workspaces/skypilot/sky/check.py", line 41, in check_one_cloud
      ok, reason = cloud.check_credentials()
    File "/workspaces/skypilot/sky/clouds/do.py", line 264, in check_credentials
      except do.exceptions().HttpResponseError as err:
    File "/workspaces/skypilot/sky/adaptors/common.py", line 64, in wrapper
      m.load_module()
    File "/workspaces/skypilot/sky/adaptors/common.py", line 36, in load_module
      raise ImportError(self._import_error_message) from e
  ImportError: Failed to import dependencies for DO. Try pip install "skypilot[do]"
  ```
  
  ```
    OCI: disabled                              
      Reason: Missing credential file at ~/.oci/config. For more details, refer to: https://docs.skypilot.co/en/latest/getting-started/installation.html#oracle-cloud-infrastructure-oci
    Paperspace: disabled                              
      Reason: Failed to access Paperspace Cloud with credentials.
      To configure credentials, follow the instructions at: https://docs.skypilot.co/en/latest/getting-started/installation.html#paperspace
      Generate API key and create a json at `~/.paperspace/config.json` with 
           {"apiKey": "[YOUR API KEY]"}
      Reason: Credentials not found
  ```
  
  
  <!-- If relevant, fill in versioning info to help us troubleshoot -->
  _Version & Commit info:_
  * `sky -v`: PLEASE_FILL_IN
  * `sky -c`: PLEASE_FILL_IN
  