[issue35734] Remove unused _BaseV4._is_valid_netmask in ipaddress

ulin added the comment: OK, message copied, I'll mark it closed. :) -- resolution: -> not a bug stage: patch review -> resolved status: open -> closed ___ Python tracker <https://bugs.pyth

[issue35734] ipaddress's _BaseV4._is_valid_netmask fails to detect invalid netmask like 255.254.128.0

New submission from ulin : valid netmask like 255.0.0.0 255.128.0.0, but 255.254.128.0 is not valid, but ipaddress._BaseV4._is_valid_netmask fails to detect the latter. Tested in Python 3.6.7, as the code stays the same, affects all after Python 3.6.7. -- components: Library (Lib