Modify python xvfbwrapper

- install through pip instead of apt

travis2bash.sh

@@ -89,7 +89,6 @@ function pyqt5() {
     # install pyqt5 on python > 3
     if [[ ! "$TRAVIS_PYTHON" == "2.7" ]]; then
         sudo apt -y install qtbase5-dev qt5-default
-        sudo apt -y install python3-xvfbwrapper
     fi
 }
 
@@ -200,6 +199,9 @@ if [[ "$(declare -p travis_python)" =~ "declare -a" ]]; then
             virtualenv_init "$ppath" "$pv"
         fi
         virtualenv_activate "$pv"
+        if [[ ! "$TRAVIS_PYTHON" == "2.7" ]]; then
+            pip install xvfbwrapper
+        fi
         python_run "$ppath" "$pv"
         deactivate
     done