[PATCH] testbot/UpdateTaskLogs: Fix error handling for the task.log and testbot.log renames.

[Francois Gouget]

The code checks that the target filename does not exist (so rename()
does not clobber it), so it's very unlikely that the error is that the
destination already exists.

Signed-off-by: Francois Gouget 
---
 testbot/bin/UpdateTaskLogs | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/testbot/bin/UpdateTaskLogs b/testbot/bin/UpdateTaskLogs
index d89ccfc4ad..f259302a20 100755
--- a/testbot/bin/UpdateTaskLogs
+++ b/testbot/bin/UpdateTaskLogs
@@ -351,12 +351,17 @@ sub ProcessTaskLogs($$$)
       "old_log.err" => "old_testbot.log");
     while (my ($OldName, $NewName) = each %LogMap)
     {
-      if (-f "$TaskDir/$OldName" and !-f "$TaskDir/$NewName" and
-          !rename("$TaskDir/$OldName", "$TaskDir/$NewName"))
+      next if (!-f "$TaskDir/$OldName");
+      if (-f "$TaskDir/$NewName")
       {
         Error TaskKeyStr($Task) .": Could not rename $OldName because $NewName already exists\n";
         $Rc = 1;
       }
+      elsif (!rename("$TaskDir/$OldName", "$TaskDir/$NewName"))
+      {
+        Error TaskKeyStr($Task) .": Could not rename $OldName to $NewName: $!\n";
+        $Rc = 1;
+      }
     }

# testbot.log is the only log which we expect to be empty.