title: Firefox cannot open "libgtk-3.so.0". How to circumvent?
body: <p>I have two CentOS VMs which use Jenkins to run automated tests through firefox. Both have firefox installed. Both versions of firefox are the same (firefox-56.0.1). I do not know if they are both x86_64 or some other type, but whichever they are, they are the same. (I am using the same .tar.bz2 file. I copied it from one instance to the other.)</p>
  
  <p>In one instance, I am able to run firefox. "firefox --headless" returns "*** You are running in headless mode."</p>
  
  <p>After copying the .tar.bz2 file to the other instance and installing firefox, I find that the new instance does not have the same performance. "firefox --headless" returns the following:</p>
  
  <pre><code>XPCOMGlueLoad error for file /usr/local/firefox/libmozgtk.so:
  libgtk-3.so.0: cannot open shared object file: No such file or directory
  Couldn't load XPCOM.
  </code></pre>
  
  <p>What might explain this difference? It appears that I did something right in the first instance, but I cannot tell what. Is there some setting that will prevent firefox from trying to use the "libgtk-3.so.0" file? This file does not exist on either instance.</p>
  
  <p>I've seen this question elsewhere, but the answer seems to focus on versions (I know my version has worked in the first instance) and a particular bug that has been backlogged (this bug only bothers me for the new instance).</p>