Keep pip in the debian image (#356)

build_debian.sh

@@ -166,6 +166,7 @@ sudo LANG=C chroot $FILESYSTEM_ROOT apt-get -y install      \
 ## Note: gdisk is needed for sgdisk in install.sh
 ## Note: parted is needed for partprobe in install.sh
 ## Note: ca-certificates is needed for easy_install
+## Note: don't install python-apt by pip, older than Debian repo one
 sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install      \
     file                    \
     ifupdown                \
@@ -232,8 +233,7 @@ set /files/etc/sysctl.conf/net.ipv6.conf.all.accept_dad 0
 ## docker-py is needed by Ansible docker module
 sudo LANG=C chroot $FILESYSTEM_ROOT easy_install pip
 sudo LANG=C chroot $FILESYSTEM_ROOT pip install 'docker-py==1.6.0'
-## Remove pip which is unnecessary in the base image
-sudo LANG=C chroot $FILESYSTEM_ROOT pip uninstall -y pip
+## Note: keep pip installed for maintainance purpose
 
 ## Config DHCP for eth0
 sudo tee -a $FILESYSTEM_ROOT/etc/network/interfaces > /dev/null <<EOF

files/build_templates/sonic_debian_extension.j2

@@ -56,6 +56,7 @@ sudo mkdir -p $FILESYSTEM_ROOT/etc/sonic/
 sudo mkdir -p $FILESYSTEM_ROOT/usr/share/sonic/templates/
 
 # Install dependencies for SONiC config engine
+# TODO: pip-install instead of apt-get after config engine wrapped into a wheel, even better use pip implicitly installing dependencies
 sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install \
     python-lxml    \
     python-jinja2  \