[3.6] bpo-25862: Fix assertion failures in io.TextIOWrapper.tell(). (GH-3918)#8012

serhiy-storchaka merged 1 commit intopython:3.6python/cpython:3.6from

ZackerySpytz:backport-23db935-3.6ZackerySpytz/cpython:backport-23db935-3.6Copy head branch name to clipboard