Deprecator overrides global warnings

[iandanforth-alation]

Describe the bug
This line attempts to restore the previous state of warnings which is changed on line 42. Unfortunately it assumes that the previous state is 'default' which is not always the case. If you have elsewhere set ENV variables to define your python warnings behavior this will override them.

This bug was surfaced by this commit
Your environment

Linux-3.10.0-957.12.2.el7.x86_64-x86_64-with-centos-7.7.1908-Core
('Python', '2.7.15 (default, Dec 11 2018, 21:06:48) \n[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)]')
('pyfakefs', '3.7.2')

[mrbean-bremen]

Thanks - good catch! Will probably have a look tonight.