astroid 2.3.1

Release Date: 2019-09-30

• A transform for the builtin dataclasses module was added.

  This should address various dataclasses issues that were surfaced
  even more after the release of pylint 2.4.0.
  In the previous versions of astroid, annotated assign nodes were
  allowed to be retrieved via getattr() but that no longer happens
  with the latest astroid release, as those attribute are not actual
  attributes, but rather virtual ones, thus an operation such as getattr()
  does not make sense for them.

• Update attr brain to partly understand annotated attributes

  Close #656