character instead of truncate it.  Based on patch by Victor Stinner.

empty string or tuple argument.

On some platforms Tcl memory allocator returns NULL when allocating zero-sized
block of memory.

ckalloc() causes the Tcl interpreter to panic, attemptckalloc() returns NULL
if the memory allocation fails.

Patch from Thomas Kluyver.

First letter no longer is stripped from the "status" key in
the result of Treeview.heading().

a pipe in _ipconfig_getnode().

response is received.  Patch by Martin Panter.

Original patch by Serhiy Storchaka.

support.unlink()

support.rmtree() and support.unlink() in test_zipfile & test_tarfile

check_ssl_verifiy(), so only test_connect_using_sslcontext_verified() is
skipped if smtp.gmail.com cannot be joined, not the whole file.

implementation is broken (ex: skipped on FreeBSD 6.4).

Original patch by Lita Cho.

This platform exposes the function ioctl(FIOCLEX), but calling it fails with
errno is ENOTTY: "Inappropriate ioctl for device". set_inheritable() now falls
back to the slower fcntl() (F_GETFD and then F_SETFD).

Original patch by Josh Lynn.

There is a race condition in create_connection() used with wait_for() to have a
timeout. sock_connect() registers the file descriptor of the socket to be
notified of write event (if connect() raises BlockingIOError). When
create_connection() is cancelled with a TimeoutError, sock_connect() coroutine
gets the exception, but it doesn't unregister the file descriptor for write
event. create_connection() gets the TimeoutError and closes the socket.

If you call again create_connection(), the new socket will likely gets the same
file descriptor, which is still registered in the selector. When sock_connect()
calls add_writer(), it tries to modify the entry instead of creating a new one.

This issue was originally reported in the Trollius project, but the bug comes
from Tulip in fact (Trollius is based on Tulip):
https://bitbucket.org/enovance/trollius/issue/15/after-timeouterror-on-wait_for

This change fixes the race condition. It also makes sock_connect() more
reliable (and portable) is sock.connect() raises an InterruptedError.