It is not in the official repositories of Fedora, so to install it there are two approaches. Firstly, there is an unofficial repository for Blockify maintained by Fusion809 in the Open Build Service (OBS). It provides binaries for the latest Blockify release. Secondly, one can install Blockify in a more "from scratch" (or manual) fashion using pip.
Using the OBS
To install Blockify from Fusion809's OBS repository follow the instructions here. Unfortunately the OBS does not always have a repository for the very latest release of Fedora (e.g., there was no repository for Fedora 25 on 16 December 2016, despite Fedora 25 being released on 22 November 2016), so sometimes if one is using the latest release of Fedora may one need to use the OBS repository for the previous release of Fedora.
Manual installation with pip
To install Blockify manually using pip one first needs to install the dependencies with DNF, such as using the command:
sudo dnf install pygtk2 python3-docopt dbus pulseaudio alsa-lib-devel gstreamer-devel python3-pip
To be safe it would be advisable to upgrade pip3 to the latest version (as the version of pip in Fedora's repositories tends to lag behind the latest) using:
sudo pip3 install --upgrade pip
as sometimes Blockify's installation may require the very latest pip. Then run:
sudo pip3 install git+https://github.com/serialoverflow/blockify
to install Blockify. Odds are one will want a desktop configuration file (so one can launch it from one's application menu), if so run:
echo -e '[Desktop Entry]\nName=Blockify\nComment=Blocks Spotify commercials\nExec=blockify-ui\nIcon='$(python3 -c 'import pkg_resources; print(pkg_resources.resource_filename("blockify", "data/icon-red-512.png"))')'\nType=Application\nCategories=AudioVideo' | sudo tee /usr/share/applications/blockify.desktop