'Constructor.
Args:
what: Either \'file\' or \'blob\' or \'errorblob\' indicating what kind of
objects this batcher uploads.  Used in messages and URLs.
logging_context: The _ClientDeployLoggingContext for this upload.'

def __init__(self, what, logging_context):

    assert (what in ('file', 'blob', 'errorblob')), repr(what)
    self.what = what
    self.logging_context = logging_context
    self.single_url = ('/api/appversion/add' + what)
    self.batch_url = (self.single_url + 's')
    self.batching = True
    self.batch = []
    self.batch_size = 0
