try to change debootstrap mirror

.travis.yml

@@ -3,7 +3,7 @@ before_install:
 - sudo apt-get install -y cmake liblog4cpp5-dev liblivemedia-dev libasound2-dev
 - sudo apt-get install -y qemu-user-static debootstrap 
 - host mirrors.kernel.org
-- sudo debootstrap --variant=minbase --arch armhf --foreign --include=g++,liblog4cpp5-dev,liblivemedia-dev,libasound2-dev jessie rootfs http://sfo-korg-mirror.kernel.org
+- sudo debootstrap --variant=minbase --arch armhf --foreign --include=g++,liblog4cpp5-dev,liblivemedia-dev,libasound2-dev jessie rootfs http://sfo-korg-mirror.kernel.org/debian
 - sudo cp /usr/bin/qemu-arm-static rootfs/usr/bin/
 - sudo chroot rootfs /debootstrap/debootstrap --second-stage
 - git clone https://github.com/raspberrypi/tools.git rpi_tools