[3.6]bpo-15786: Fix IDLE autocomplete return problem. (#2198) by terryjreedy · Pull Request #2199 · python/cpython

Before, <return> would not, for instance, complete 're.c' to 're.compile' even with 'compile' highlighted.  Now it does.  Before, <return> was inserted into text, which in Shell meant compile() and possibly execute.  Now cursor is left after completion.
(cherry picked from commit 32fd874)