(Merge 3.4) Issue #21090: io.FileIO.readall() does not ignore I/O errors

anymore. Before, it ignored I/O errors if at least the first C call read()
succeed.

diff --cc Misc/NEWS
index 04287755fe62c0170d6fe3bb2961954ee137a828,0983a59c954719d24abff44b1cef33cd2d2c9e09..b7c7b9bbb9a392729d4796cb743219660a24acff
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -103,17 -27,11 +103,20 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #21090: io.FileIO.readall() does not ignore I/O errors anymore. Before,
+   it ignored I/O errors if at least the first C call read() succeed.
+ 
 +- Issue #5800: headers parameter of wsgiref.headers.Headers is now optional.
 +  Initial patch by Pablo Torres Navarrete and SilentGhost.
 +
  - Issue #21781: ssl.RAND_add() now supports strings longer than 2 GB.
  
 +- Issue #21679: Prevent extraneous fstat() calls during open().  Patch by
 +  Bohuslav Kabrda.
 +
 +- Issue #21863: cProfile now displays the module name of C extension functions,
 +  in addition to their own name.
 +
  - Issue #11453: asyncore: emit a ResourceWarning when an unclosed file_wrapper
    object is destroyed. The destructor now closes the file if needed. The
    close() method can now be called twice: the second call does nothing.

diff --cc Modules/_io/fileio.c
Simple merge