beast -citation requires X11 ??

[EricDeveaud]

Hello,

[gensoft@55c39a5bf82f beast-mcmc-1.10.5-23570d1]$ beast -citations_file foo

        BEAST v1.10.5 Prerelease #23570d1, 2002-2019
       Bayesian Evolutionary Analysis Sampling Trees
                 Designed and developed by
   Alexei J. Drummond, Andrew Rambaut and Marc A. Suchard
                              
               Department of Computer Science
                   University of Auckland
                  [email protected]
                              
             Institute of Evolutionary Biology
                  University of Edinburgh
                     [email protected]
                              
              David Geffen School of Medicine
           University of California, Los Angeles
                     [email protected]
                              
                Downloads, Help & Resources:
                  	http://beast.community
                              
Source code distributed under the GNU Lesser General Public License:
          	http://github.com/beast-dev/beast-mcmc
                              
                     BEAST developers:
	Alex Alekseyenko, Guy Baele, Trevor Bedford, Filip Bielejec, Erik Bloomquist, Matthew Hall,
	Joseph Heled, Sebastian Hoehna, Denise Kuehnert, Philippe Lemey, Wai Lok Sibon Li,
	Gerton Lunter, Sidney Markowitz, Vladimir Minin, Michael Defoin Platel,
          	Oliver Pybus, Chieh-Hsi Wu, Walter Xie
                              
                         Thanks to:
    	Roald Forsberg, Beth Shapiro and Korbinian Strimmer

Exception in thread "main" java.awt.HeadlessException: 
No X11 DISPLAY variable was set, but this program performed an operation which requires it.
	at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:204)
	at java.awt.Window.<init>(Window.java:536)
	at java.awt.Frame.<init>(Frame.java:420)
	at java.awt.Frame.<init>(Frame.java:385)
	at javax.swing.JFrame.<init>(JFrame.java:189)
	at dr.app.beast.BeastMain.main(Unknown Source)

why ?

regards

Eric