Cannot import attrs for Python 3.5 #965
Description
First of all, attrs is great, thanks to all who work on it.
On Python 3.5, the next-gen API (define, field, etc.) is not defined in attr/__init__.py, which causes an ImportError on startup. Here's a reproducer:
# python3
Python 3.5.3 (default, Dec 3 2018, 20:11:08)
[GCC 7.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import attrs
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.5/site-packages/attrs/__init__.py", line 3, in <module>
from attr import (
ImportError: cannot import name 'define'
Looks like it's happening because of these lines in attr/__init__: https://github.com/python-attrs/attrs/blob/main/src/attr/__init__.py#L76-L79
along with https://github.com/python-attrs/attrs/blob/main/src/attrs/__init__.py#L19 (which tries to import those names unconditionally).