Enable LLVM 7.0.1 test on Travis (#2955)

3 jobs for upstream in 16 seconds (queued for 28 seconds)
Status Job ID Name Coverage
  Build
failed #170
build

00:00:16

 
  Test
skipped #172
allowed to fail
code_quality
skipped #171
test
 
Name Stage Failure
failed
build Build
Checking out 28574a82 as upstream...
Skipping Git submodules setup
$ # Auto DevOps variables and functions # collapsed multi-line command
$ setup_docker
$ build
Logging to GitLab Container Registry with CI credentials...
WARNING! Using --password via the CLI is insecure. Use --password-stdin.
Error response from daemon: Get https://registry-1.docker.io/v2/: unauthorized: incorrect username or password
ERROR: Job failed: exit code 1