Running generate-values.sh on Ubuntu 20.04 raises "AttributeError"module 'argparse' has not attribute 'BooleanOptionalAction'"

[dunatotatos]

Describe the bug
I'm following the instructions here: https://renku.readthedocs.io/en/latest/how-to-guides/admin/deploying-renku.html#basic-configuration to generate the values file for deploying Renku. Running the script raises an AttributeError exception.

To Reproduce
Full console copy/paste:

ahungler@L-1010036748:~/Work/renku-values$ wget https://raw.githubusercontent.com/SwissDataScienceCenter/renku/master/scripts/generate-values/generate-values.sh
--2022-08-17 11:50:58--  https://raw.githubusercontent.com/SwissDataScienceCenter/renku/master/scripts/generate-values/generate-values.sh
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 2606:50c0:8002::154, 2606:50c0:8001::154, 2606:50c0:8000::154, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|2606:50c0:8002::154|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1038 (1.0K) [text/plain]
Saving to: ‘generate-values.sh’

generate-values.sh     100%[==========================>]   1.01K  --.-KB/s    in 0s      

2022-08-17 11:50:59 (34.8 MB/s) - ‘generate-values.sh’ saved [1038/1038]

ahungler@L-1010036748:~/Work/renku-values$ sh generate-values.sh -o renku-values.yaml
generate-values.sh: 5: [[: not found
--2022-08-17 11:51:09--  https://raw.githubusercontent.com/SwissDataScienceCenter/renku/master/scripts/generate-values/generate-values.py
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 2606:50c0:8003::154, 2606:50c0:8000::154, 2606:50c0:8001::154, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|2606:50c0:8003::154|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 4748 (4.6K) [text/plain]
Saving to: ‘generate-values.py’

generate-values.py     100%[==========================>]   4.64K  --.-KB/s    in 0s      

2022-08-17 11:51:10 (85.6 MB/s) - ‘generate-values.py’ saved [4748/4748]

--2022-08-17 11:51:10--  https://raw.githubusercontent.com/SwissDataScienceCenter/renku/master/scripts/generate-values/base-renku-values.yaml.template
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 2606:50c0:8003::154, 2606:50c0:8000::154, 2606:50c0:8001::154, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|2606:50c0:8003::154|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2845 (2.8K) [text/plain]
Saving to: ‘base-renku-values.yaml.template’

base-renku-values.yaml 100%[==========================>]   2.78K  --.-KB/s    in 0s      

2022-08-17 11:51:10 (69.5 MB/s) - ‘base-renku-values.yaml.template’ saved [2845/2845]

--2022-08-17 11:51:10--  https://raw.githubusercontent.com/SwissDataScienceCenter/renku/master/scripts/generate-values/requirements.txt
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 2606:50c0:8003::154, 2606:50c0:8000::154, 2606:50c0:8001::154, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|2606:50c0:8003::154|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 27 [text/plain]
Saving to: ‘requirements.txt’

requirements.txt       100%[==========================>]      27  --.-KB/s    in 0s      

2022-08-17 11:51:10 (932 KB/s) - ‘requirements.txt’ saved [27/27]

virtual environment not found, creating one...
Requirement already satisfied: virtualenv in /usr/lib/python3/dist-packages (20.0.17)
created virtual environment CPython3.8.10.final.0-64 in 138ms
  creator CPython3Posix(dest=/home/ahungler/Work/renku-values/.venv-renku-values, clear=False, global=False)
  seeder FromAppData(download=False, pip=latest, setuptools=latest, wheel=latest, pkg_resources=latest, via=copy, app_data_dir=/home/ahungler/.local/share/virtualenv/seed-app-data/v1.0.1.debian.1)
  activators BashActivator,CShellActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator
Collecting ruamel.yaml
  Downloading ruamel.yaml-0.17.21-py3-none-any.whl (109 kB)
     |████████████████████████████████| 109 kB 3.8 MB/s 
Collecting prompt-toolkit
  Downloading prompt_toolkit-3.0.30-py3-none-any.whl (381 kB)
     |████████████████████████████████| 381 kB 3.9 MB/s 
Collecting ruamel.yaml.clib>=0.2.6; platform_python_implementation == "CPython" and python_version < "3.11"
  Downloading ruamel.yaml.clib-0.2.6-cp38-cp38-manylinux1_x86_64.whl (570 kB)
     |████████████████████████████████| 570 kB 3.9 MB/s 
Collecting wcwidth
  Downloading wcwidth-0.2.5-py2.py3-none-any.whl (30 kB)
Installing collected packages: ruamel.yaml.clib, ruamel.yaml, wcwidth, prompt-toolkit
Successfully installed prompt-toolkit-3.0.30 ruamel.yaml-0.17.21 ruamel.yaml.clib-0.2.6 wcwidth-0.2.5

----------------------------
| Configuring Renku values |
----------------------------
Traceback (most recent call last):
  File "generate-values.py", line 147, in <module>
    main()
  File "generate-values.py", line 52, in main
    action=argparse.BooleanOptionalAction, default=False
AttributeError: module 'argparse' has no attribute 'BooleanOptionalAction'

Run environment (please complete the following information):

• local terminal
• Other: local terminal
• renku-python version ?
• browser N/A

Running on Ubuntu 20.04

Additional context
I suspect this is due to the python version used on Ubuntu 20.04:

Python 3.8.10