Issue #27539: Merge from 3.5.

diff --cc Lib/fractions.py
Simple merge

diff --cc Lib/test/test_fractions.py
Simple merge

diff --cc Misc/ACKS
Simple merge

diff --cc Misc/NEWS
index cefe83102beca9575c2e6b9722623d9e5e553e79,7530624751b6be3a0f4d9b46df17ce8be3d6b8af..ff677e008ed63c90fc5aedae198aca8b13282a86
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -35,56 -22,17 +35,59 @@@ Core and Builtin
    In a brand new thread, raise a RuntimeError since there is no active
    exception to reraise. Patch written by Xiang Zhang.
  
 -- Issue #27419: Standard __import__() no longer look up "__import__" in globals
 -  or builtins for importing submodules or "from import".  Fixed handling an
 -  error of non-string package name.
 +Library
 +-------
  
 -- Issue #27083: Respect the PYTHONCASEOK environment variable under Windows.
++- Issue #27539: Fix unnormalised ``Fraction.__pow__`` result in the case
++  of negative exponent and negative base.
+ 
 -- Issue #27514: Make having too many statically nested blocks a SyntaxError
 -  instead of SystemError.
 +- Issue #21718: cursor.description is now available for queries using CTEs.
  
 -- Issue #27473: Fixed possible integer overflow in bytes and bytearray
 -  concatenations.  Patch by Xiang Zhang.
 +- Issue #27819: In distutils sdists, simply produce the "gztar" (gzipped tar
 +  format) distributions on all platforms unless "formats" is supplied.
 +
 +- Issue #2466: posixpath.ismount now correctly recognizes mount points which
 +  the user does not have permission to access.
 +
 +- Issue #9998: On Linux, ctypes.util.find_library now looks in LD_LIBRARY_PATH
 +  for shared libraries.
 +
 +- Issue #12713: Allowed abbreviation of subcommands by end-users for users of
 +  argparse.
 +
 +Tests
 +-----
 +
 +- Issue #27787: Call gc.collect() before checking each test for "dangling
 +  threads", since the dangling threads are weak references.
 +
 +
 +What's New in Python 3.6.0 alpha 4
 +==================================
 +
 +*Release date: 2016-08-15*
 +
 +Core and Builtins
 +-----------------
 +
 +- Issue #27704: Optimized creating bytes and bytearray from byte-like objects
 +  and iterables.  Speed up to 3 times for short objects.  Original patch by
 +  Naoki Inada.
 +
 +- Issue #26823: Large sections of repeated lines in tracebacks are now
 +  abbreviated as "[Previous line repeated {count} more times]" by the builtin
 +  traceback rendering. Patch by Emanuel Barry.
 +
 +- Issue #27574: Decreased an overhead of parsing keyword arguments in functions
 +  implemented with using Argument Clinic.
 +
 +- Issue #22557: Now importing already imported modules is up to 2.5 times
 +  faster.
 +
 +- Issue #17596: Include <wincrypt.h> to help with Min GW building.
 +
 +- Issue #17599: On Windows, rename the privately defined REPARSE_DATA_BUFFER
 +  structure to avoid conflicting with the definition from Min GW.
  
  - Issue #27507: Add integer overflow check in bytearray.extend().  Patch by
    Xiang Zhang.