docker build fails

[cmatKhan]

On Ubuntu 20.04

The docker build fails with this message:

> docker build -t teaser_git . && docker run -v $(pwd):/teaser -it teaser_git "/usr/bin/teaser_shell.sh"
Sending build context to Docker daemon  18.23MB
Step 1/3 : FROM ubuntu
latest: Pulling from library/ubuntu
405f018f9d1d: Pull complete 
Digest: sha256:b6b83d3c331794420340093eb706a6f152d9c1fa51b262d9bf34594887c2c7ac
Status: Downloaded newer image for ubuntu:latest
 ---> 27941809078c
Step 2/3 : RUN apt-get update && apt-get install -y wget zlib1g-dev cmake && apt-get install -y python python-pip git && pip install --upgrade pip==9.0.3 && pip install intervaltree tornado pyaml psutil numpy
 ---> Running in 91c293837a44
...
Updating certificates in /etc/ssl/certs...
0 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d...
done.
Reading package lists...
Building dependency tree...
Reading state information...
Package python is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
  python2-minimal python2 dh-python 2to3 python-is-python3

E: Package 'python' has no installation candidate
The command '/bin/sh -c apt-get update && apt-get install -y wget zlib1g-dev cmake && apt-get install -y python python-pip git && pip install --upgrade pip==9.0.3 && pip install intervaltree tornado pyaml psutil numpy' returned a non-zero code: 100