Can't install pyOpenSSL for Python 3

I am running a Pyhon3 script that depends on OpenSSL and it depends on OpenSSL. However, I am having problems installing it.

# pip3 install pyOpenSSL
Downloading/unpacking pyOpenSSL
  Downloading pyOpenSSL-17.4.0-py2.py3-none-any.whl (52kB): 52kB downloaded
Requirement already satisfied (use --upgrade to upgrade): six>=1.5.2 in /usr/lib/python3/dist-packages (from pyOpenSSL)
Downloading/unpacking cryptography>=1.9 (from pyOpenSSL)
  Downloading cryptography-2.1.3.tar.gz (441kB): 441kB downloaded
  Running setup.py (path:/tmp/pip-build-ljoosnix/cryptography/setup.py) egg_info for package cryptography
    error in cryptography setup command: Invalid environment marker: python_version < '3'
    Complete output from command python setup.py egg_info:
    error in cryptography setup command: Invalid environment marker: python_version < '3'

----------------------------------------
Cleaning up...
Command python setup.py egg_info failed with error code 1 in /tmp/pip-build-ljoosnix/cryptography
Storing debug log for failure in /root/.pip/pip.log

I'm not sure what that "Invalid environment marker" means. Does it mean I can't install this for Python 3?

This is for a Debian 8 VM.

Solution

Try to run sudo apt-get install libssl-dev

Upd: Try to run sudo pip3 install --upgrade pip