storage: Fix false error message visiting home page

When visiting homepage as a non-admin user, don't throw an error into the
console about not being able to get root partition information. This is a
regression from refactoring during backups change.

Fixes: #1468.

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

plinth/modules/backups/views.py

@@ -143,9 +143,11 @@ class UploadArchiveView(SuccessMessageMixin, FormView):
         context['title'] = _('Upload and restore a backup file')
         context['subsubmenu'] = subsubmenu
         try:
-            disk_info = storage.get_disk_info('/', self.request)
-        except (PlinthError, PermissionError):
-            logger.error('Error getting information about root partition.')
+            disk_info = storage.get_disk_info('/')
+        except PlinthError as exception:
+            logger.exception(
+                'Error getting information about root partition: %s',
+                exception)
         else:
             # The maximum file size that can be uploaded and restored is at
             # most half of the available disk space:

plinth/modules/storage/__init__.py

@@ -142,14 +142,13 @@ def get_filesystem_type(mount_point='/'):
     raise ValueError('No such mount point')
 
 
-def get_disk_info(mountpoint, request):
+def get_disk_info(mount_point):
     """Get information about the free space of a drive"""
-    if not is_user_admin(request, cached=True):
-        raise PermissionError
     disks = get_disks()
-    list_root = [disk for disk in disks if disk['mountpoint'] == mountpoint]
+    list_root = [disk for disk in disks if disk['mountpoint'] == mount_point]
     if not list_root:
-        raise PlinthError
+        raise PlinthError('Mount point {} not found.'.format(mount_point))
+
     percent_used = list_root[0]['percent_used']
     free_bytes = list_root[0]['free']
     free_gib = free_bytes / (1024**3)

plinth/modules/storage/views.py

@@ -32,7 +32,7 @@ from django.views.decorators.http import require_POST
 from plinth import actions
 from plinth.errors import PlinthError
 from plinth.modules import storage
-from plinth.utils import format_lazy
+from plinth.utils import format_lazy, is_user_admin
 
 from . import get_disk_info, get_error_message
 
@@ -91,10 +91,14 @@ def expand_partition(request, device):
 
 def warn_about_low_disk_space(request):
     """Warn about insufficient space on root partition."""
+    if not is_user_admin(request, cached=True):
+        return
+
     try:
-        root_info = get_disk_info('/', request)
-    except (PlinthError, PermissionError):
-        logger.error('Error getting information about root partition.')
+        root_info = get_disk_info('/')
+    except PlinthError as exception:
+        logger.exception('Error getting information about root partition: %s',
+                         exception)
         return
 
     message = format_lazy(