(Merge 3.4) Issue #19884: readline: Disable the meta modifier key if stdout is

not a terminal to not write the ANSI sequence "\033[1034h" into stdout. This
sequence is used on some terminal (ex: TERM=xterm-256color") to enable support
of 8 bit characters.

diff --cc Misc/NEWS
index e95528f5859d689a71a90878c556e8f3d6c7aba3,0def1949a77f31831e5909564e9c45dfcea44626..e6ad54f3fb0df537da77c8ea7329e57e09a743ef
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -108,15 -27,11 +108,20 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #19884: readline: Disable the meta modifier key if stdout is not
+   a terminal to not write the ANSI sequence "\033[1034h" into stdout. This
+   sequence is used on some terminal (ex: TERM=xterm-256color") to enable
+   support of 8 bit characters.
+ 
 +- Issue #4350: Removed a number of out-of-dated and non-working for a long time
 +  Tkinter methods.
 +
 +- Issue #6167: Scrollbar.activate() now returns the name of active element if
 +  the argument is not specified.  Scrollbar.set() now always accepts only 2
 +  arguments.
 +
 +- Issue #15275: Clean up and speed up the ntpath module.
 +
  - Issue #21888: plistlib's load() and loads() now work if the fmt parameter is
    specified.