typing: suppress a bunch of potential import-error cases in extensions...
typing: suppress a bunch of potential import-error cases in extensions
As flagged by pytype locally. Either the ImportError is locally handled, or the
imported module was previously determined to be present by `hgave` (for the
phabricator extension), or is handled by the `hgext.convert.subversion` module
when imported (for the `hgext.convert.transport` module).