TestAccessControlWithSSLCertDir fails on macOS

After merging !291 (merged) the TestAccessControlWithSSLCertDir fails while running tests locally on macOS with x509: certificate signed by unknown authority

        helpers_test.go:32: time="2020-07-06T10:10:25+10:00" level=error msg="Fetching access token failed" error="Post \"https://127.0.0.1:64166/oauth/token\": x509: certificate signed by unknown authority" host=nonexistent.gitlab-example.com path=/auth redirect_uri="https://nonexistent.gitlab-example.com/subgroup/nonexistent/" state="m0-t3-6RIaW1u-iU3jrqKg=="
        helpers_test.go:32: nonexistent.gitlab-example.com 127.0.0.1 - - [2020/07/06:10:10:25 +1000] "GET /auth?code=1&state=m0-t3-6RIaW1u-iU3jrqKg== HTTP/1.1" 503 2904 "" "Go-http-client/1.1" 101
        acceptance_test.go:1559:
            	Error Trace:	acceptance_test.go:1559
            	Error:      	Not equal:
            	            	expected: 302
            	            	actual  : 503
            	Test:       	TestAccessControlWithSSLCertDir/[subgroup]_no_project_should_redirect_to_login_and_then_return_404#01
FAIL