Log Message:
Changes 16.3.0:
* Attributes now can have user-defined metadata which greatly improves \ 
attrs‘s extensibility.

* Allow for a __attrs_post_init__ method that – if defined – will get \ 
called at the end of the attrs-generated __init__ method.

* Add @attr.s(str=True) that will optionally create a __str__ method that is \ 
identical to __repr__. This is mainly useful with Exceptions and other classes \ 
that rely on a useful __str__ implementation but overwrite the default one \ 
through a poor own one. Default Python class behavior is to use __repr__ as \ 
__str__ anyways.

If you tried using attrs with Exceptions and were puzzled by the tracebacks: \ 
this option is for you.

* Don’t overwrite __name__ with __qualname__ for attr.s(slots=True) classes.