Isolate tests from personal Readline init files using INPUTRC=/dev/null trick

Author: johnslavik

Lib/test/support/pty_helper.py

@@ -10,11 +10,22 @@
 
 from test.support.import_helper import import_module
 
-def run_pty(script, input=b"dummy input\r", env=None):
+def run_pty(script, input=b"dummy input\r", env=None, readline=None):
     pty = import_module('pty')
     output = bytearray()
     [master, slave] = pty.openpty()
     args = (sys.executable, '-c', script)
+
+    if readline is None:
+        readline = "readline" in sys.modules
+    if readline:
+        # Isolate readline from personal init files by setting INPUTRC
+        # to an empty file. See also GH-142353.
+        if env is None:
+            env = {**os.environ.copy(), "INPUTRC": os.devnull}
+        else:
+            env.setdefault("INPUTRC", os.devnull)
+
     proc = subprocess.Popen(args, stdin=slave, stdout=slave, stderr=slave, env=env)
     os.close(slave)
     with ExitStack() as cleanup: