retry code until it succeeeds

 Tenacity is a general-purpose retrying library to simplify the task of adding
 retry behavior to just about anything. It originates from a fork of Retrying.
 .
 Features:
  * Generic Decorator API
  * Specify stop condition (i.e. limit by number of attempts)
  * Specify wait condition (i.e. exponential backoff sleeping between attempts)
  * Customize retrying on Exceptions
  * Customize retrying on expected returned result