Instead of the dependency oriented logic, switch to print them
for each package or name needed. Might give a bit more readable
errors now. There's still few corner cases that proper error is
not output, which are cought by the test cases.
Solver will now never report partial solution where a conflict
constraint is not satisfied. The is because with --force we might
install the partial solution; and if conflicted packages were to
be installed we might have extra trouble.
Timo Teräs