Update Dockerfile

Dockerfile

@@ -47,7 +47,11 @@ RUN git clone https://github.com/pyenv/pyenv.git /builder/.pyenv && \
     PYTHON_CONFIGURE_OPTS="--enable-shared" pyenv install --force 3.6.4
 
 USER root
-RUN curl -L https://download.qt.io/official_releases/qt/5.9/5.9.4/qt-opensource-linux-x64-5.9.4.run --output qt-opensource-linux-x64-5.9.4.run && \
+RUN export XVFBARGS="-screen 0 1280x1024x24" && \
+    export DISPLAY=:99.0  && \
+    sh -e /etc/init.d/xvfb start  && \
+    sleep 3  && \
+    curl -L https://download.qt.io/official_releases/qt/5.9/5.9.4/qt-opensource-linux-x64-5.9.4.run --output qt-opensource-linux-x64-5.9.4.run && \
     chmod +x qt-opensource-linux-x64-5.9.4.run && \
     ./qt-opensource-linux-x64-5.9.4.run --script ./qt-installer-noninteractive.qs