AttributeError: module 'simplejson' has no attribute 'loads'

[maravento]

SO: Ubuntu 18.04.4
Commands:
git clone https://github.com/UnaPibaGeek/ctfr.git
cd ctfr
pip3 install -r requirements.txt

which python3.6 python pip3 pip
/usr/bin/python3.6
/usr/bin/python
/home/user/.local/bin/pip3
/home/user/.local/bin/pip

pip3 --version
pip 19.2.3 from /home/user/.local/lib/python3.6/site-packages/pip (python 3.6)

python3 ctfr.py -d google.com -o outfile

Error:
Traceback (most recent call last):
File "ctfr.py", line 77, in <module>
main()
File "ctfr.py", line 61, in main
for (key,value) in enumerate(req.json()):
File "/home/user/.local/lib/python3.6/site-packages/requests/models.py", line 888, in json
return complexjson.loads(
AttributeError: module 'simplejson' has no attribute 'loads'

works with:

python ctfr.py -d google.com -o outfile