I get this error on a fresh install of gitlab. The message looks like:
fatal: unable to access 'https://gitlab-ci-
token:xxxxxxxxxxxxxxxxxxxx@gitlab.example.com/something.git/': Peer's
Certificate issuer is not recognized.ERROR: Job
failed: exit status 1
Looks like a self signed certificate where the host is verified on TLS handshake. Since the original question is 2 years old, please provide more insights into your installation (versions, logs, CI configuration).