[Asdf-devel] bug1335323 reveals another bug....

[Robert P. Goldman]

It turns out that caching negative results from FIND-SYSTEM search
overrides the ERROR-P option to FIND-SYSTEM.  If ERROR-P is T, but a NIL
result is found in the cache, FIND-SYSTEM will return the NIL instead of
raising a MISSING-COMPONENT error.

I have just pushed a new test-cache.script that fails because of this bug.

I will try to fix this tomorrow -- it's a little tricky, the logic is
baked into WITH-ASDF-CACHE, I believe.  FIND-SYSTEM will have to get
refactored to move the error-handling outside WITH-ASDF-CACHE.