Install magenta in python3.5 on Debian 9.3:
1.install setuptools:
apt-get install python3-setuptools
apt install python3-dev
apt-get install libasound2-dev
apt-get install libjack-dev
2.install pip3.5:
tar xf pip-9.0.1.tar.gz
cd pip-9.0.1
python3.5 setup.py install
3.install
python3.5 install magenta