handle inexistent packages properly

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
make crashes of AUR-dependency-builds not get stuff to die completely

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
do not crash when -Syu is run in a non-tty

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>