Try workaround for test issues in #21425

Lib/test/script_helper.py

@@ -86,6 +86,14 @@ def spawn_python(*args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, **kw):
     """
     cmd_line = [sys.executable, '-E']
     cmd_line.extend(args)
+    # Under Fedora (?), GNU readline can output junk on stderr when initialized,
+    # depending on the TERM setting.  Setting TERM=vt100 is supposed to disable
+    # that.  References:
+    # - http://reinout.vanrees.org/weblog/2009/08/14/readline-invisible-character-hack.html
+    # - http://stackoverflow.com/questions/15760712/python-readline-module-prints-escape-character-during-import
+    # - http://lists.gnu.org/archive/html/bug-readline/2007-08/msg00004.html
+    env = kw.setdefault('env', {})
+    env.setdefault('TERM', 'vt100')
     return subprocess.Popen(cmd_line, stdin=subprocess.PIPE,
                             stdout=stdout, stderr=stderr,
                             **kw)