When download a github content, it thows following error:
"ERROR: certificate ....To connect to raw.github.com insecurely, use `--no-check-certificate'"

Problem:

+ Unset valid time/timezone.
+ CA Certificate invalid.

Resolve:

+ Set valid datetime.
+ Reinstall CA Certificate.
+ Set global parameter --no-check-certificate for every requests:

`echo "check_certificate = off" >> ~/.wgetrc`