‘python3.5’: No such file or directory

I try to install my machine learning environment ( install all the library that I need) using Dockerfile :
Here is the dockerfile :

# Build an image that can do training and inference in SageMaker
# This is a Python 2 image that uses the nginx, gunicorn, flask stack
# for serving inferences in a stable way.

FROM ubuntu:16.04

MAINTAINER Amazon AI <[email protected]>

RUN apt-get -y update && apt-get install -y --no-install-recommends 
    && rm -rf /var/lib/apt/lists/*

# Here we get all python packages.
# There's substantial overlap between scipy and numpy that we eliminate by
# linking them together. Likewise, pip leaves the install caches populated which uses
# a significant amount of space. These optimizations save a fair amount of space in the
# image, which reduces start up time.
RUN wget https://bootstrap.pypa.io/get-pip.py && python get-pip.py && 
    pip install numpy scipy scikit-learn pandas flask gevent gunicorn && 
        (cd /usr/local/lib/python2.7/dist-packages/scipy/.libs; rm *; ln ../../numpy/.libs/* .) && 
        rm -rf /root/.cache

# Set some environment variables. PYTHONUNBUFFERED keeps Python from buffering our standard
# output stream, which means that logs can be delivered to the user quickly. PYTHONDONTWRITEBYTECODE
# keeps Python from writing the .pyc files which are unnecessary in this case. We also update
# PATH so that the train and serve programs are found when the container is invoked.

ENV PATH="/opt/program:${PATH}"

# Set up the program in the image
COPY xgboost /opt/program
WORKDIR /opt/program

But I get this error :

/usr/bin/env: 'python3.5': No such file or directory

Can you help me to solve this problem please?

Thank you

Source: StackOverflow