Unable to run demo in hyperparameter optimization

**Describe the bug**
HPO demo https://federatedscope.io/docs/use-hpo/

**To Reproduce**
Steps to reproduce the behavior:
https://federatedscope.io/docs/use-hpo/#an-hands-on-exercise
```
python federatedscope/hpo.py --cfg scripts/example_configs/toy_rs.yaml
```

**Expected behavior**
https://federatedscope.io/docs/use-hpo/#an-hands-on-exercise

**Screenshots**
```
2024-01-25 10:55:55,376 (cfg_fl_setting:221)WARNING: We found the number of gpu is insufficient, thus cfg.federate.process_num=0
Traceback (most recent call last):
File "/Users/xxf/code/FederatedScope/federatedscope/hpo.py", line 34, in
update_logger(init_cfg, clear_before_add=True)
File "/Users/xxf/code/FederatedScope/federatedscope/core/auxiliaries/logging.py", line 125, in update_logger
f" {socket.gethostbyname(socket.gethostname())}")
socket.gaierror: [Errno 8] nodename nor servname provided, or not known
```

**Desktop (please complete the following information):**
- OS: Mac
- Version 14.2.1

Start with federatedscope/hpo.py at line 34 and federatedscope/core/auxiliaries/logging.py at line 125, then run the documented command with scripts/example_configs/toy_rs.yaml. Check the HPO demo instructions and verify that the demo runs on the reported Mac environment without the socket.gaierror.

Written by the indexing model from the issue text.