wireproto: port protocol handler to zope.interface
zope.interface is superior to the abc module. Let's port to it.
As part of this, we add tests for interface conformance for
classes implementing the interface.
Differential Revision: https://phab.mercurial-scm.org/D2983
#require docutils gettext
Error: the current ro localization has some rst defects exposed by
moving pager to core. These two warnings about references are expected
until the localization is corrected.
$ $TESTDIR/check-gendoc ro
checking for parse errors
gendoc.txt:58: (WARNING/2) Inline interpreted text or phrase reference start-string without end-string.
gendoc.txt:58: (WARNING/2) Inline interpreted text or phrase reference start-string without end-string.