exception documentation

indicates an API that is in 'legacy' status, a long term deprecation.

Inherited from Base20DeprecationWarning:

Method __str__ Undocumented
Class Variable deprecated_since Indicates the version that started raising this deprecation warning

Inherited from HasDescriptionCode (via Base20DeprecationWarning, SADeprecationWarning):

Method __init__ Undocumented
Instance Variable code Undocumented
Method _code_str Undocumented