message: Fix incorrect handling of empty key URI in AWS KMS.
diff: @@ -51,8 +51,10 @@ class AwsKmsClient(object):
  """
  match = re.match('aws-kms://arn:aws:kms:([a-z0-9-]+):', key_uri)
  - if match:
  - self.key_uri = key_uri
  + if not key_uri:
  + self._key_uri = ''
  + elif match:
  + self._key_uri = key_uri
  else:
  raise core.TinkError
  