add yumrepo_core module to fixtures

Author: bastelfreak

.fixtures.yml

@@ -2,3 +2,6 @@ fixtures:
   repositories:
     apt:    "https://github.com/puppetlabs/puppetlabs-apt.git"
     stdlib: "https://github.com/puppetlabs/puppetlabs-stdlib.git"
+    yumrepo_core:
+      repo: https://github.com/puppetlabs/puppetlabs-yumrepo_core.git
+      puppet_version: ">= 6.0.0"