Comment # 4 on bug 954921 from Martin Pluskal

Also note that, when you install slack on openSUSE:
sudo zypper in ./slack-2.0.0-0.1.fc21.x86_64.rpm 
Loading repository data...
Reading installed packages...
Resolving package dependencies...

Problem: nothing provides libXScrnSaver needed by slack-2.0.0-0.1.fc21.x86_64
 Solution 1: do not install slack-2.0.0-0.1.fc21.x86_64
 Solution 2: break slack-2.0.0-0.1.fc21.x86_64 by ignoring some of its
dependencies

When you choose option 2 (ignore some of its dependencies), it works just fine.