swarmbucket: fix empty dimension value

appengine/cr-buildbucket/swarming/swarmingcfg.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import json
 import re
 
 from proto import project_config_pb2
 
 
@@ skipping 12 matching lines @@
 
 
 def validate_dimensions(field_name, dimensions, ctx):
   known_keys = set()
   for i, dim in enumerate(dimensions):
     with ctx.prefix('%s #%d: ', field_name, i + 1):
       components = dim.split(':', 1)
       if len(components) != 2:
         ctx.error('does not have ":"')
         continue
-      key, value = components
+      key, _ = components
       if not key:
         ctx.error('no key')
       else:
         if not DIMENSION_KEY_RGX.match(key):
           ctx.error(
             'key "%s" does not match pattern "%s"',
             key, DIMENSION_KEY_RGX.pattern)
         if key in known_keys:
           ctx.error('duplicate key %s', key)
         else:
           known_keys.add(key)
-      if not value:
-        ctx.error('no value')
 
 
 def validate_recipe_cfg(recipe, common_recipe, ctx):
   common_recipe = common_recipe or project_config_pb2.Swarming.Recipe()
   if not (recipe.name or common_recipe.name):
     ctx.error('name unspecified')
   if not (recipe.repository or common_recipe.repository):
     ctx.error('repository unspecified')
   validate_recipe_properties(recipe.properties, recipe.properties_j, ctx)
 
@@ skipping 75 matching lines @@
       validate_recipe_properties(
           swarming.common_recipe.properties,
           swarming.common_recipe.properties_j, ctx)
 
   for i, b in enumerate(swarming.builders):
     with ctx.prefix('builder %s: ' % (b.name or '#%s' % (i + 1))):
       validate_builder_cfg(
           b, ctx, bucket_has_pool_dim=has_pool_dim,
           common_recipe=common_recipe)
 
+
 def has_pool_dimension(dimensions):
   return any(d.startswith('pool:') for d in dimensions)