unification of meta-attributes handling:
* remove has_format, has_text_encoding, format, text_encoding methods on Entity
* remove rich_text_fields method on EntitySchema
* use instead has_metadata / meta_attribute on EntitySchema (from yams)
and attribute_metadata on Entity
class RepoThread(object):
def __init__(self, *args):
pass # XXX raise
def start(self):
pass
def join(self):
pass
class LoopTask(RepoThread):
def cancel(self):
pass