[gimp-web] tools: flush stdout after each mirror check.

[Jehan <jehanp src gnome org>]

commit edc7e097045a79ec2f43922c8422075c328f45bd
Author: Jehan <jehan girinstud io>
Date:   Sun May 1 11:42:28 2022 +0200

    tools: flush stdout after each mirror check.
    
    While on my terminal, it's happening this way, obviously it isn't on
    whatever backend uses the CI. Flushing the output allows to verify the
    script is not stuck or anything. It's running, simply each of these
    checks take time.

 tools/downloads/gimp-check-mirrors.py | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/tools/downloads/gimp-check-mirrors.py b/tools/downloads/gimp-check-mirrors.py
index 041169f7..2e51e972 100755
--- a/tools/downloads/gimp-check-mirrors.py
+++ b/tools/downloads/gimp-check-mirrors.py
@@ -161,6 +161,7 @@ for local_uri in local_uris:
             except OSError as error:
                 error_count += 1
                 print(str(error.strerror) + ' : ' + mirror_uri)
+            sys.stdout.flush()
         print()
 
 if error_count == 0: