tests: remove all assets before test_asset_slots_management (#24453)

tests/test_manager.py

@@ -2,6 +2,7 @@ import base64
 import json
 import os
 import re
+import shutil
 import StringIO
 import urllib
 
@@ -656,6 +657,8 @@ def test_asset_management_search(app, admin_user):
 def test_asset_slots_management(app, admin_user):
     app = login(app)
 
+    if os.path.exists(default_storage.path('uploads')):
+        shutil.rmtree(default_storage.path('uploads'))
     assert Asset.objects.count() == 0
 
     with override_settings(COMBO_ASSET_SLOTS={'collectivity:banner': {'label': 'Banner'}}):