[verify_layer] Remove buildbot as optional and make required.

BLD-161

Change-Id: I2be0246a7fc1ac4e62baf3210c8309fbcf8e8b78
diff --git a/packages/verify_layer.py b/packages/verify_layer.py
index ded12ec..fe3e173 100755
--- a/packages/verify_layer.py
+++ b/packages/verify_layer.py
@@ -15,16 +15,12 @@
 
 # Standard names for root packages in a layer.
 ROOT_CANONICAL_PACKAGES = [
+    'buildbot',
     'default',
     'dev',
     'kitchen_sink',
 ]
 
-# Standard names for optional root packages in a layer.
-ROOT_OPTIONAL_PACKAGES = [
-    'buildbot',
-]
-
 # Standard names for packages in a layer.
 CANONICAL_PACKAGES = [
     'all',
@@ -105,7 +101,7 @@
                 return False
             return True
         for file in filenames:
-            if is_root and (file in ROOT_CANONICAL_PACKAGES or file in ROOT_OPTIONAL_PACKAGES or file == layer):
+            if is_root and (file in ROOT_CANONICAL_PACKAGES or file == layer):
                 continue
             if file in CANONICAL_PACKAGES or file in NON_PACKAGE_FILES:
                 continue