mail: let all charset values be native strings
Charset values will typically be used to build email.header.Header
instances, which takes str (though it tolerates bytes) or passed to
decode()/encode() methods of string values (which want str). It seems
that using native str involves less conversions than before and this
also helps type hinting (as illustrates removal of pytype disabling
instructions).
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)