The result of host() was not empty when the network is constructed by a tuple containing an
integer mask and only 1 bit left for addresses.

Original patch by Jon Foster and Berker Peksag.

If the class has a member that's a MemberDescriptorType, it's not a default value, it's from that member being in __slots__.

If a non-dataclass derives from a frozen dataclass, allow attributes to be set.
Require either all of the dataclasses in a class hierarchy to be frozen, or all non-frozen.
Store `@dataclass` parameters on the class object under `__dataclass_params__`. This is needed to detect frozen base classes.

This reverts commit ac317700.

(Reverts only the lib2to3 part.)

It was actually fixed in SQLite 3.8.8, not 3.8.7.

Multi-phase initialized modules allow m_traverse to be called while the
module is still being initialized, so module authors may need to account
for that.

(cherry picked from commit e32bbaf376a09c149fa7c7f2919d7c9ce4e2a055)

Creating backup files with ~ suffix can be undesirable in some environment,
such as when building RPM packages. Instead of requiring the user to remove
those files manually, option -n was added, that simply disables this feature.

-n was selected because 2to3 has the same option with this behavior.

New tests also added.

I also made the comments in line with the builtin Grammar/Grammar. PEP 306 was
withdrawn, Kees Blom's railroad program has been lost to the sands of time for
at least 16 years now (I found a python-dev post from people looking for it).

Co-authored-by: Vajrasky Kok <sky.kok@speaklikeaking.com>

fstat may block for long time if the file descriptor is on a
non-responsive NFS server, hanging all threads. Most fstat() calls are
handled by _Py_fstat(), releasing the GIL internally, but but
_Py_fstat_noraise() does not release the GIL, and most calls release the
GIL explicitly around it.

This patch fixes last 2 calls to _Py_fstat_no_raise(), avoiding hangs
when calling:
- mmap.mmap()
- os.urandom()
- random.seed()

In some conditions the standard streams will be None or closed in the child process (for example if using "pythonw" instead of "python" on Windows).  Avoid failing with a non-0 exit code in those conditions.

Report and initial patch by poxthegreat.

consisting of non-constants: `x in [a, b]` and `for x in [a, b]`.
The case of all constant elements already was optimized.

and remove redundant code.