Hello, sorry for late reply, I've been on vacation.

But, looks like last cherry-pick from Amy's branch broke that token caching you're talking about.
Here's my task JSON:

{
"SwiftObjects.create_object_then_download_object_and_delete_object" :[
{                                                                                                                                                                             
  "runner": {                              
    "type": "constant",                    
    "concurrency": 5,                      
    "times": 10                            
  },                                                                  
  "args": {                                
    "container_name": "interia-test",
    "object_size": 8192,                   
    "objects_per_container": 1000          
  },                                                                    
  "context": {                             
    "users": {                             
      "cache_tokens": True
    }                                                                                  
  }                                                                                    
}    
]
}

Don't bother about that task name - it's a custom task created only to test whole CRUD chain at once, not for public use ATM.

But when I'm trying to run task with "cache_tokens": True, the schema validation fails:

Subtask SwiftObjects.create_object_then_download_object_and_delete_object[0] has wrong configuration                                                                          
Subtask configuration:                     
{"runner": {"type": "constant", "concurrency": 5, "times": 10}, "args": {"container_name": "interia-test", "object_size": 8192, "objects_per_container": 1000}, "context": {"users": {"cache_tokens": true}}}            

Reason(s):                                 
 {"cache_tokens": true} is valid under each of {'additionalProperties': False, 'description': 'Use existing users and tenants.', 'properties': {'user_choice_method': {'$ref': '#/definitions/user_choice_method'}, 'cache_tokens': {'$ref': '#/definitions/cache_tokens'}}}, {'additionalProperties': False, 'description': 'Create new temporary users and tenants.', 'properties': {'user_domain': {'type': 'string', 'description': 'ID of domain in which users will be created.'}, 'project_domain': {'type': 'string', 'description': 'ID of domain in which projects will be created.'}, 'cache_tokens': {'$ref': '#/definitions/cache_tokens'}, 'user_choice_method': {'$ref': '#/definitions/user_choice_method'}, 'users_per_tenant': {'minimum': 1, 'type': 'integer', 'description': 'The number of users to create per one tenant.'}, 'tenants': {'minimum': 1, 'type': 'integer', 'description': 'The number of tenants to create.'}, 'resource_management_workers': {'minimum': 1, 'type': 'integer', 'description': 'The number of concurrent threads to use for serving users context.'}}}                   

Failed validating 'oneOf' in schema:       
    {'$schema': 'http://json-schema.org/draft-04/schema',                              
     'definitions': {'cache_tokens': {'description': 'Option to cache tokens in user context',                                                                                
                                      'type': 'boolean'},                              
                     'user_choice_method': {'description': 'The mode of balancing usage of users between scenario iterations.',                                               
                                            'enum': ['random',                         
                                                     'round_robin']}},                 
     'oneOf': [{'additionalProperties': False,                                         
                'description': 'Create new temporary users and tenants.',              
                'properties': {'cache_tokens': {'$ref': '#/definitions/cache_tokens'}, 
                               'project_domain': {'description': 'ID of domain in which projects will be created.',                                                           
                                                  'type': 'string'},                   
                               'resource_management_workers': {'description': 'The number of concurrent threads to use for serving users context.',                           
                                                               'minimum': 1,           
                                                               'type': 'integer'},     
                               'tenants': {'description': 'The number of tenants to create.',                                                                                 
                                           'minimum': 1,                               
                                           'type': 'integer'},                         
                               'user_choice_method': {'$ref': '#/definitions/user_choice_method'},                                                                            
                               'user_domain': {'description': 'ID of domain in which users will be created.',                                                                 
                                               'type': 'string'},                      
                               'users_per_tenant': {'description': 'The number of users to create per one tenant.',                                                           
                                                    'minimum': 1,                      
                                                    'type': 'integer'}}},              
               {'additionalProperties': False,                                         
                'description': 'Use existing users and tenants.',                      
                'properties': {'cache_tokens': {'$ref': '#/definitions/cache_tokens'}, 
                               'user_choice_method': {'$ref': '#/definitions/user_choice_method'}}}],                                                                         
     'type': 'object'}                     

On instance:                               
    {"cache_tokens": true}`    

Same thing with YAML input (in fact it's converted to JSON from what I know). But when I remove the cache_tokens option, and whole "users" section, it works well, but without caching.