title: Understanding the error message: spdlog::spdlog_ex
body: <p>I am aware this question is very specific. Nontheless, maybe s.o. can help:</p>
  
  <p>I was trying to compile an open-source code today. (anyone, who's interested, <a href="https://github.com/OPENAIRINTERFACE/openair-cn/wiki/OpenAirSoftwareSupport" rel="nofollow noreferrer">that's the one</a>.) The error message described below occurs after <code>oai_hss -j $PREFIX/hss_rel14.json --onlyloadkey</code> - having followed the step-by-step installation guide to this point.
  After typing the aforementioned command in my terminal, the following error is thrown: </p>
  
  <pre><code>terminate called after throwing an instance of 'spdlog::spdlog_ex'
  what(): Failed opening file logs/hss.log for writing: No such file or directory
  Aborted (core dumped)
  </code></pre>
  
  <p>Allright, this sounds pretty severy (core dumped). I was searching google for a meaning of that error message. I came across <a href="https://github.com/gabime/spdlog/wiki/5.-Logger-registry" rel="nofollow noreferrer">this</a> other github project. Apparently the spdlog class is trying to enable logging from wherever I run my program. And it throws an spdlog_ex error whenever the file it is trying to add to the registry (in this case logs/hss.log) already exists within this registry. So, I guess, the solution to my problem would be to find this registry and delete logs/hss.log. Does this make sense? </p>
  
  <p>Question: Where the heck do I find this registry? </p>
  
  <p>Maybe some background knowledge would be useful: I am trying to compile the open-source code within a VM that is running Ubuntu 18.04.3 LTS bionic with a 4.15.0-66-generic kernel. 
  I was searching the /tmp directory for a log folder already. There is none. Where else could it be?  </p>