Set an explicit version - "8.1" isn't working, nor is "~".

geerlingguy · geerlingguy · commit bfb50bb1d8ed · 2016-07-26T21:47:47.000-05:00
diff --git a/example.drupal.make.yml b/example.drupal.make.yml
@@ -11,7 +11,7 @@ projects:
 
   # Core.
   drupal:
-    version: "~"
+    version: "8.1.7"
     # Use this if you need a working git repository of Drupal core instead of
     # the latest stable.
     # type: "core"
