NameError: global name 'sys' is not defined

[kostaskol]

OS: Kali GNU/Linux Rolling
Python version: Python 2.7.15+

There seems to be a problem with the handler of reverse shell number 1.
The complete error is:

[+] Port Already used by another Program or Something Wrong... 2018 ./extras/c-ares-1.6.0/ares_gethostbyaddr.lo                                                                                             
Traceback (most recent call last):
  File "/usr/local/bin/shellpop", line 858, in <module>
    main()
  File "/usr/local/bin/shellpop", line 840, in main
    sys.exit()
NameError: global name 'sys' is not defined

The command I executed was:

$ shellpop --reverse --number 1 --handler --host xx.xx.xx.xx --port xxxx 

It gave me an initial shell and after executing find, I got this error and the shell closed.

I am available for any more info.
Thanks in advance