$ dnf download --source nicotine+
$ sudo dnf build-dep nicotine+-3.3.4-1.fc40.src.rpm
$ rpm -ivh nicotine+-3.3.4-1.fc40.src.rpm
$ cd ~/rpmbuild/SOURCES
$ vi SPECS/nicotine+.spec [bump the release from 1 to 2]
$ cd SOURCES
$ tar -zxvf nicotine+-3.3.4.tar.gz
$ cd nicotine-plus-3.3.4/pynicotine/plugins/leech_detector

modify __init__.py to have:
            subprocess.run(["notify-send", "Nicotine+", "A leecher is downloading""])
added near the line that says:
"Leecher detected, %s is only sharing

around '"Leecher detected, %s is only sharing'
and at the top add:
import subprocess

$ cd ../../../../
$ rm nicotine+-3.3.4.tar.gz
$ tar -zcvf nicotine+-3.3.4.tar.gz nicotine-plus-3.3.4
$ cd ..
$ rpmbuild -bb SPECS/nicotine+.spec
$ cd RPMS/noarch
$ sudo rpm -Uvh nicotine+-3.3.4-2.fc40.noarch.rpm