Todo: fix python-telegram installation

[nlhomme]

Step 9/19 : RUN pip3 install --user python-telegram
 ---> Running in 6705ff76e201
Collecting python-telegram
  Downloading https://files.pythonhosted.org/packages/6d/88/e6d70e74ae7febcfdf56431cff93aa4851f1d758114f1bd4ebd808d2c609/python-telegram-0.12.0.tar.gz (11.8MB)
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
    ModuleNotFoundError: No module named 'setuptools'
    
    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-nrgvanm6/python-telegram/
The command '/bin/sh -c pip3 install --user python-telegram' returned a non-zero code: 1

[nlhomme]

=> create a requirement.txt file to prevent futur errors