Thread method isAlive compatible with python 3.9

[dmknght]

• Faraday GTK Client version: 1.1.0
• Python version: 3.9
• Operating System: Parrot OS 4.10

Description

On Debian testing based distro, thee default python has been upgraded to python3.9 which removed isAlive(). It makes application failed to stop (crashes after click on exit)

What I Did

• Start Faraday-client
• Stop faraday client
• Client has this error while stopping

Original exception was:
Traceback (most recent call last):
  File "/usr/bin/faraday-client", line 11, in <module>
    load_entry_point('faraday-client==1.0.0', 'console_scripts', 'faraday-client')()
  File "/usr/lib/python3/dist-packages/faraday_client/start_client.py", line 448, in main
    start_faraday_client()
  File "/usr/lib/python3/dist-packages/faraday_client/start_client.py", line 227, in start_faraday_client
    exit_status = start()
  File "/usr/lib/python3/dist-packages/faraday_client/model/application.py", line 129, in start
    return self.__exit(exit_code)
  File "/usr/lib/python3/dist-packages/faraday_client/model/application.py", line 141, in __exit
    if self._model_controller.isAlive():
TypeError: 'NoneType' object is not callable

Link: https://bugs.python.org/issue37804

Fix method is edit isAlive() to is_alive() at https://github.com/infobyte/faraday-client/blob/master/faraday_client/model/application.py#L141
It worked well with python3.9.
It should be compatible with python2 (doc: https://docs.python.org/2.7/library/threading.html) and any older version of python3 (doc: https://docs.python.org/3.5/library/threading.html)