make python3-venv package generic

Author: Vladimir Kotal

dev/before_install

@@ -7,7 +7,7 @@ if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
 		exit 1
 	fi
 
-	sudo apt-get install -qq cvs git mercurial cssc bzr subversion monotone rcs rcs-blame python3 python3.4-venv python3-pip nodejs
+	sudo apt-get install -qq cvs git mercurial cssc bzr subversion monotone rcs rcs-blame python3 python3-venv python3-pip nodejs
 	if [[ $? != 0 ]]; then
 		echo "cannot install extra packages"
 		exit 1