sudo pip3 install pdfminer.six

I changed the shebang line This works on ubuntu for python3
from: /usr/bin/env: ‘python\r’
to : /usr/bin/env: ‘python3\r’

But this still didn't solve the issue. I had to convert the file from dos format to unix format.
sudo apt-get install dos2unix

and then find the file by
whereis pdf2txt.py
and then convert the file to unix format
sudo dos2unix pathto(pdf2txt.py)