catch lockContentForRemoval exception

removeKey should not throw exceptions, so catch exception there

In Assistant.Unused, keep trying to drop other keys if one drop fails

Annex/Content.hs

@@ -220,6 +220,8 @@ lockContentShared key a = lockContentUsing lock key $ ifM (inAnnex key)
 
 {- Exclusively locks content, while performing an action that
  - might remove it.
+ -
+ - If locking fails, throws an exception rather than running the action.
  -}
 lockContentForRemoval :: Key -> (ContentRemovalLock -> Annex a) -> Annex a
 lockContentForRemoval key a = lockContentUsing lock key $ 

Assistant/Unused.hs

@@ -75,7 +75,7 @@ expireUnused duration = do
 	let oldkeys = M.keys $ M.filter (tooold now) m
 	forM_ oldkeys $ \k -> do
 		debug ["removing old unused key", key2file k]
-		liftAnnex $ do
+		liftAnnex $ tryNonAsync $ do
 			lockContentForRemoval k removeAnnex
 			logStatus k InfoMissing
   where

Remote/Git.hs

@@ -377,7 +377,9 @@ keyUrls gc repo r key = map tourl locs'
 dropKey :: Remote -> State -> Key -> Annex Bool
 dropKey r st key = do
 	repo <- getRepo r
-	dropKey' repo r st key
+	catchNonAsync
+		(dropKey' repo r st key)
+		(\e -> warning (show e) >> return False)
 
 dropKey' :: Git.Repo -> Remote -> State -> Key -> Annex Bool
 dropKey' repo r (State connpool duc _) key