Error: Can't open display: :1

[Fribb]

When I start your docker file (with docker-compose) I get the error message

ok: down: openbox: 1s, normally up, want up
Error: Can't open display: :1
Error: Can't open display: :1
Nov 25, 2017 1:37:12 PM org.apache.catalina.core.StandardContext postWorkDirectory
WARNING: Failed to create work directory [/var/lib/tomcat7/work/Catalina/localhost/guacamole] for context [/guacamole]
Error: Can't open display: :1
Openbox-Message: Failed to open the display from the DISPLAY environment variable.
Invalid geometry "1280"x"720"
use: X [:] [option]

Any idea?