Add implicit unblocks for t-p-u approvals

Signed-off-by: Adam D. Barratt <adam@adam-barratt.org.uk>

t-p-u approval previously required both an "unblock" and an "approve"
hint if the package was blocked; the "approve" should be sufficient and
this is the simplest method of achieving that.

There are some cases where this does not quite do the right thing (e.g.
for a package which has both a t-p-u "approve" hint and an "unblock"
hint for the package in unstable) but it is preferable to requiring
t-p-u hints to be added in pairs always.

britney.py

@@ -802,6 +802,10 @@ class Britney:
         if len(hints["block"]) == 0 and len(hints["block-udeb"]) == 0:
             self.__log("WARNING: No block hints at all, not even udeb ones!", type="W")
 
+        # A t-p-u approval overrides an unstable block
+        for p in hints["approve"]:
+            hints["unblock"][p] = hints["approve"][p]
+
         return hints
 
     def write_heidi(self, filename):