Make it clear what lockfile could not be acquired.

ChangeLog

@@ -3,6 +3,8 @@ version 1.0 -- UNRELEASED
 	mysql:
 	 . Use --skip-events when backing up the performance_schema database.
 	   (Closes: #673572)
+    backupninja changes
+	 . Make it clear what lockfile could not be acquired, if any.
 
 version 1.0-rc1 -- May 15, 2012
     handler changes

src/backupninja.in

@@ -349,7 +349,7 @@ function process_action() {
 
        else
 	   # a backup is probably ongoing already, so display an error message
-	   debug "failed to acquire lock"
+	   debug "failed to acquire lock $lockfile"
 	   echo "Fatal: Could not acquire lock $lockfile. A backup is probably already running for $file." >>$bufferfile
        fi
    } 200> $lockfile