storage: Don't log exception of disk space check fails

When running inside a container, it is not possible to retrieve information
about the disk that is mounted on '/'. Ignore errors in such cases.

Tests performed:

- Inside a container, start the service using freedombox-devel. Every 3 minutes
a check for disk space will be done in developer mode. If UDisks is being used
as source of information, the free space check will fail with an error logged.

- With the changes, the error is not shown.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Tested-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/modules/storage/__init__.py

@@ -290,9 +290,7 @@ def warn_about_low_disk_space(request):
 
     try:
         root_info = get_disk_info('/')
-    except PlinthError as exception:
+    except PlinthError:
-        logger.exception('Error getting information about root partition: %s',
-                         exception)
         return
 
     show = False