- update to 2.1.1:
* Fixed typo 'marking' instead of 'marketing' in case-
insensitive mailbox name list.
* When DNS-based deliverability checks fail, in some cases
exceptions are now thrown with `raise ... from` for better
nested exception tracking.
* Fixed tests to work when no local resolver can be configured.
* This project is now licensed under the Unlicense (instead of
CC0).
* Minor improvements to tests.
* Minor improvements to code style.
- drop dont-require-resolv-tests.patch: obsolete

* Ignore warning as error from requests-toolbelt via dnspython.