Issue #18315: Improve fileinput docs by adding 'bufsize' where missing and
replacing redundant signature in input() docstring with one-line summary.
Original patch by Terrel Shumway.
Issue *18081, #18242: Change Idle warnings capture in PyShell and run to stop
replacing warnings.formatwarnings and to reverse replacement of
warnings.showwarnings when import is complete and when main function exits.
Add test_warning.py. Vinay Sajip provided capture_warnings function.
Issue #18237: Fix assertRaisesRegexp error caought by Jeff Tratner.