Back out fix for issue #13886; it introduced a new bug in interactive readline use.

Lib/test/test_builtin.py

@@ -20,13 +20,6 @@ try:
     import pty, signal
 except ImportError:
     pty = signal = None
-# Importing this module has the side-effect of changing the behavior of input().
-# Ensure that we always use the readline version (if available), so we don't get
-# different results depending on what other tests have already imported.
-try:
-    import readline
-except ImportError:
-    pass
 
 
 class Squares:

Misc/NEWS

@@ -15,10 +15,6 @@ Core and Builtins
 
 - Issue #16979: Fix error handling bugs in the unicode-escape-decode decoder.
 
-- Issue #13886: Fix input() to not strip out input bytes that cannot be decoded
-  using the locale encoding. Also fix sporadic failures in test_builtin due to
-  dependence on whether the readline module has previously been imported.
-
 - Issue #16772: The base argument to the int constructor no longer accepts
   floats, or other non-integer objects with an __int__ method.  Objects
   with an __index__ method are now accepted.

Modules/readline.c

@@ -1063,7 +1063,7 @@ call_readline(FILE *sys_stdin, FILE *sys_stdout, char *prompt)
     char *saved_locale = strdup(setlocale(LC_CTYPE, NULL));
     if (!saved_locale)
         Py_FatalError("not enough memory to save locale");
-    setlocale(LC_CTYPE, "C");
+    setlocale(LC_CTYPE, "");
 #endif
 
     if (sys_stdin != rl_instream || sys_stdout != rl_outstream) {