io in Client constructor

`etcd3.client.Client` performs IO in its constructor

https://github.com/kragniz/python-etcd3/blob/aca9b60205620e31b1635ce32b7ef74170698c7e/etcd3/client.py#L127

https://github.com/kragniz/python-etcd3/blob/aca9b60205620e31b1635ce32b7ef74170698c7e/etcd3/client.py#L148

this makes it difficult to create an asyncio port or a thread based wrapper

is it safe to call `.__enter__()` and `.__exit__` in different threads?

Start by reading etcd3/client.py at the linked lines 127 and 148 to trace the I/O performed during Client construction and the related context-manager methods. Check the issue's thread for the intended lifecycle and thread-safety expectations; done should establish whether construction and __enter__/__exit__ can support the proposed asyncio or thread-based wrapper safely.

Written by the indexing model from the issue text.