Bench init Error unsupported operand type(s) for +: 'NoneType' and 'list'

Hello I’am new at ERPNext . I installed frappe recently in Ubuntu 16.04 ,I try the installation from Installation but the command
bench init frappe-bench return an error . I do this steps :
git clone GitHub - frappe/bench: CLI to manage Multi-tenant deployments for Frappe apps bench-repo
pip install --user -e bench-repo
cd ~
bench init frappe-bench
Error :

guesmi@guesmi-X555LD:~/frappe-bench$ bench init frappe-bench
/home/guesmi/.local/lib/python2.7/site-packages/requests/ RequestsDependencyWarning: Old version of cryptography ([1, 2, 3]) may cause slowdown.
warnings.warn(warning, RequestsDependencyWarning)
WARN: bench is installed in editable mode!

This is not the recommended mode of installation for production. Instead, install the package from PyPI with: pip install frappe-bench

Traceback (most recent call last):
File “/home/guesmi/.local/bin/bench”, line 11, in
load_entry_point(‘frappe-bench’, ‘console_scripts’, ‘bench’)()
File “/home/guesmi/bench-repo/bench/”, line 45, in cli
if sys.argv[1] in get_frappe_commands() + [“–site”, “–verbose”, “–force”, “–profile”]:
TypeError: unsupported operand type(s) for +: ‘NoneType’ and ‘list’
any help please

Try this first and then do init bench later

I do it but same thing

What does bench --version return?

The instructions here might be a bit more up to date, and Ubuntu 16 is no longer supported so updating to 18 may also be advisable.

bench version 5.1.0

Try: bench update --requirements

Thanks a lot all of you I resolved the problem by this steps The Hitchhiker's Guide to Installing Frappe on Linux · frappe/frappe Wiki · GitHub