bpo-32155: Bugfixes found by flake8 F841 warnings (#4619)

* turtledemo: wait until macOS osascript command completes to not
  create a zombie process
* Tools/scripts/treesync.py: declare 'default_answer' and
  'create_files' as globals to modify them with the command line
  arguments. Previously, -y, -n, -f and -a options had no effect.

flake8 warning: "F841 local variable 'p' is assigned to but never
used".

Lib/turtledemo/__main__.py

@@ -136,7 +136,7 @@ class DemoWindow(object):
             import subprocess
             # Make sure we are the currently activated OS X application
             # so that our menu bar appears.
-            p = subprocess.Popen(
+            subprocess.run(
                     [
                         'osascript',
                         '-e', 'tell application "System Events"',

Tools/scripts/treesync.py

@@ -33,7 +33,7 @@ write_slave = "ask"
 write_master = "ask"
 
 def main():
-    global always_no, always_yes
+    global default_answer, always_no, always_yes, create_files
     global create_directories, write_master, write_slave
     opts, args = getopt.getopt(sys.argv[1:], "nym:s:d:f:a:")
     for o, a in opts: