Issue #9509: make argarse properly handle IOErrors raised by argparse.FileType. Approved by Georg in the tracker.

Original patch by Michal Nowikowski, with some additions and wording
fixes by me.

I changed the wording from 'Performs a stat system call' to 'Performs
the equivalent of a stat system call', since on Windows there are no
stat/lstat system calls involved.  I also extended Michal's breakout
of the attributes into a list to the other paragraphs, and rearranged
the order of the paragraphs in the 'stat' docs to make it flow
better and put it in what I think is a more logical/useful order.

function set. Otherwise a Python fatal error about hitting an unrecoverable
recursion depth gets triggered.

Closes issue #10985. Code review by Georg Brandl.

#10983: fix several bugs in the _tunnel implementation that seem to have missed while porting between branches.  A unittest is needed!

headers with iso-8859-1 (latin1) encoding.  It was already doing that for
incoming headers which makes this behaviour now consistent in both incoming and
outgoing direction.

This makes the implementation of PEP 3333 compliant servers on top of
BaseHTTPServer possible.

zipimport uses ASCII encoding instead of cp497 to decode filenames, at
bootstrap, if the codec registry is not ready yet. It is still possible to have
non-ASCII filenames using the Unicode flag (UTF-8 encoding) for file entries in
the ZIP file.

length.  Initial patch by Ross Lagerwall.

This fixes a regression introduced by r88022.