Issue #29290: Merge 3.5.

diff --cc Lib/argparse.py
Simple merge

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

diff --cc Misc/NEWS
index d829a56b282a5745b485e9aa9cb69c2e26e240aa,d2a839054546c096f0cae81f97f239b52682e032..c72755915e02ffb27bad95221ad6db26d14957b5
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -47,10 -13,12 +47,13 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #29290: Fix a regression in argparse that help messages would wrap at
+   non-breaking spaces.
+ 
  - Issue #28735: Fixed the comparison of mock.MagickMock with mock.ANY.
  
 -- Issue #29011: Fix an important omission by adding Deque to the typing module.
 +- Issue #29316: Restore the provisional status of typing module, add
 +  corresponding note to documentation. Patch by Ivan L.
  
  - Issue #29219: Fixed infinite recursion in the repr of uninitialized
    ctypes.CDLL instances.