Where to find geckodriver needed by Selenium Python package?

Find the latest release for your OS.

Extract it, and copy geckodriver to /usr/local/bin -- so if v0.11.1 was the most recent version, and you were on 64bit linux, you'd do this:

export GECKO_DRIVER_VERSION='v0.24.0'
wget https://github.com/mozilla/geckodriver/releases/download/$GECKO_DRIVER_VERSION/geckodriver-$GECKO_DRIVER_VERSION-linux64.tar.gz
tar -xvzf geckodriver-$GECKO_DRIVER_VERSION-linux64.tar.gz
rm geckodriver-$GECKO_DRIVER_VERSION-linux64.tar.gz
chmod +x geckodriver
cp geckodriver /usr/local/bin/

Now your trial run should work.

Ubuntu 16.04+:

sudo apt-get install firefox-geckodriver