Verified in 5.7.0.16, I used a random repository from internal Gitlab which has such certificate, I then proceeded to import it with verifying the certificate which failed as expected, but when the checkbox was unchecked, it recognized the git repository and continued.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHBA-2017-0012.html