I had this problem happen to me before when I was using Ubuntu, at the time I didn't figure out what the problem was, but I solved it with ln -s /dev/null .xsessions-errors and called it quits. Today however, it happened to me on my Fedora system. However this time I figured it out.
Earlier today I had installed Oracle's sqldeveloper, I tried to lunch it a couple times from the GUI, when that failed I went to the console and typed "sqldeveloper", I was graced with the following message:
Error: /bin/java not found
Type the full pathname of a J2SE installation (or Ctrl-C to quit), the path will be stored in ~/.sqldeveloper/jdk
So I gave it my JAVA_HOME, set some config file so it would ignore the fact that I was using open-jdk and voilá.
Seven hours later I'm getting no disk space errors, wtf?
Scan tells me that my music folder is the biggest file system hog.... sure I can understand that, but it's not like it's growing right now...
Open up the console, ll -ash and bam! .xsession-erros is 11G!
I tail the file and the oracle's lovely error message and input request is being written on that file at monitor-flickering speed.
The command ps -aux reveled to me that I had 3 instances of sqldeveloper open since morning, killed those and the file stopped being written on.
Now just removed it and all is well.
TL;DR: Bad Oracle! BAD!