add some useful output to C10shell pbuilder hook

pbuilder/hooks/C10shell

 #!/bin/sh
 # invoke shell if build fails.
 
-apt-get install -y --force-yes vim less bash
+if [ "$EDITOR" = "" ]; then
+    EDITOR="vim-tiny"
+fi
+
+echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+echo "!!!!                                  !!!!"
+echo "!!!!           **FTBFS**              !!!!"
+echo "!!!!                                  !!!!"
+echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+echo ""
+echo "DROPPING TO SHELL"
+echo ""
+
+apt-get install -y --force-yes $EDITOR less bash
+if [ "$?" != "0" ]; then
+    apt-get install -y --force-yes vim-tiny less bash
+fi
+
 cd /tmp/buildd/*/debian/..
+
+echo ""
+echo ""
+echo "Use ... dpkg-buildpackage -us -uc -nc ... to restart build."
+echo ""
+echo "Please note that this will not copy the debs outside this chroot,"
+echo "if you want them, you will have to copy them yourself."
+echo ""
+echo "To invoke any hook use /tmp/hooks/NAMEOFHOOK."
+echo ""
+echo ""
+
 /bin/bash < /dev/tty > /dev/tty 2> /dev/tty