Support 'atest host mod' with '--skylab'

BUG=chromium:840039
TEST='atest host mod --skylab'
CQ-DEPEND=CL:1063124

Change-Id: Iad6a6350ce7771b0257eaa19a653635bfd6bdbbd
Reviewed-on: https://chromium-review.googlesource.com/1062942
Reviewed-by: Prathmesh Prabhu <[email protected]>
Tested-by: Ningning Xia <[email protected]>
Commit-Queue: Ningning Xia <[email protected]>
diff --git a/cli/skylab_utils.py b/cli/skylab_utils.py
index 83dbd32..1e5fb5c 100644
--- a/cli/skylab_utils.py
+++ b/cli/skylab_utils.py
@@ -41,6 +41,11 @@
     return INTERNAL_GERRIT_HOST_URL + '/' + str(change_number)
 
 
+def get_cl_message(change_number):
+    return ('Please submit the CL at %s to make the change effective.' %
+            get_cl_url(change_number))
+
+
 def construct_commit_message(subject, bug=None, test=None):
     """Construct commit message for skylab inventory repo commit.