Here's a reproducer:

[centos@undercloud test]$ cat a.py
#!/usr/bin/env python3
print('a import keystoneclient')
import keystoneclient.v3 as ksclient
import os
import subprocess


def launch():
    print('a launch()')
    p = os.getcwd()
    cmd = ['sudo', '--preserve-env', 'python3', '{}/b.py'.format(p)]
    try:
        print('a subprocess')
        subprocess.check_call(cmd)
    except Exception as e:
        print('a exception')
        raise

if __name__ == '__main__':
    print('a main()')
    launch()
[centos@undercloud test]$ cat b.py
#!/usr/bin/env python3
print('b importing keystone client')
import keystoneclient.v3 as ksclient


def launch():
    print("b launch()")

if __name__ == '__main__':
    print('b main()')
    launch()

This can result in something like this:

[centos@undercloud test]$ ./a.py
a import keystoneclient
a main()
a launch()
a subprocess
b importing keystone client
^CTraceback (most recent call last):
  File "/home/centos/test/b.py", line 3, in <module>
    import keystoneclient.v3 as ksclient
  File "/usr/lib/python3.6/site-packages/keystoneclient/v3/__init__.py", line 2, in <module>
    from keystoneclient.v3.client import Client  # noqa
  File "/usr/lib/python3.6/site-packages/keystoneclient/v3/client.py", line 23, in <module>
    from keystoneclient import httpclient
  File "<frozen importlib._bootstrap>", line 1020, in _handle_fromlist
  File "/usr/lib/python3.6/site-packages/keystoneclient/__init__.py", line 72, in __getattr__
    return importlib.import_module('keystoneclient.%s' % name)
  File "/usr/lib64/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "/usr/lib/python3.6/site-packages/keystoneclient/httpclient.py", line 43, in <module>
    import keyring
  File "/usr/lib/python3.6/site-packages/keyring/__init__.py", line 1, in <module>
    from .core import (
  File "/usr/lib/python3.6/site-packages/keyring/core.py", line 192, in <module>
    init_backend()
  File "/usr/lib/python3.6/site-packages/keyring/core.py", line 96, in init_backend
    filter(limit, backend.get_all_keyring()),
  File "/usr/lib/python3.6/site-packages/keyring/util/__init__.py", line 22, in wrapper
    func.always_returns = func(*args, **kwargs)
  File "/usr/lib/python3.6/site-packages/keyring/backend.py", line 219, in get_all_keyring
    return list(rings)
  File "/usr/lib/python3.6/site-packages/keyring/util/__init__.py", line 33, in suppress_exceptions
    for callable in callables:
  File "/usr/lib/python3.6/site-packages/keyring/util/properties.py", line 26, in __get__
    return self.fget.__get__(None, owner)()
  File "/usr/lib/python3.6/site-packages/keyring/backend.py", line 68, in viable
    cls.priority
  File "/usr/lib/python3.6/site-packages/keyring/util/properties.py", line 26, in __get__
    return self.fget.__get__(None, owner)()
  File "/usr/lib/python3.6/site-packages/keyring/backends/SecretService.py", line 40, in priority
    bus = secretstorage.dbus_init()
  File "/usr/lib/python3.6/site-packages/secretstorage/__init__.py", line 37, in dbus_init
    connection = connect_and_authenticate()
  File "/usr/lib/python3.6/site-packages/jeepney/integrate/blocking.py", line 102, in connect_and_authenticate
    conn = DBusConnection(sock)
  File "/usr/lib/python3.6/site-packages/jeepney/integrate/blocking.py", line 40, in __init__
    hello_reply = self.bus_proxy.Hello()
  File "/usr/lib/python3.6/site-packages/jeepney/integrate/blocking.py", line 84, in inner
    return self._connection.send_and_get_reply(msg)
  File "/usr/lib/python3.6/site-packages/jeepney/integrate/blocking.py", line 67, in send_and_get_reply
    self.recv_messages()
  File "/usr/lib/python3.6/site-packages/jeepney/integrate/blocking.py", line 55, in recv_messages
    b = self.sock.recv(4096)
KeyboardInterrupt
a exception
Traceback (most recent call last):
  File "/usr/lib64/python3.6/subprocess.py", line 289, in call
    return p.wait(timeout=timeout)
  File "/usr/lib64/python3.6/subprocess.py", line 1477, in wait
    (pid, sts) = self._try_wait(0)
  File "/usr/lib64/python3.6/subprocess.py", line 1424, in _try_wait
    (pid, sts) = os.waitpid(self.pid, wait_flags)
KeyboardInterrupt

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "./a.py", line 21, in <module>
    launch()
  File "./a.py", line 14, in launch
    subprocess.check_call(cmd)
  File "/usr/lib64/python3.6/subprocess.py", line 306, in check_call
    retcode = call(*popenargs, **kwargs)
  File "/usr/lib64/python3.6/subprocess.py", line 291, in call
    p.kill()
  File "/usr/lib64/python3.6/subprocess.py", line 1610, in kill
    self.send_signal(signal.SIGKILL)
  File "/usr/lib64/python3.6/subprocess.py", line 1600, in send_signal
    os.kill(self.pid, sig)
PermissionError: [Errno 1] Operation not permitted
[centos@undercloud test]$