Add test for empty bang behavior

Also fix pep8 issue

app/utils/bangs.py

@@ -61,7 +61,8 @@ def resolve_bang(query: str, bangs_dict: dict, fallback: str) -> str:
             continue
 
         bang_query = query.replace(
-            operator if operator in split_query else operator[1:] + operator[0], ''
+            operator if operator in split_query else operator[1:] +
+            operator[0], ''
         ).strip()
 
         if bang_query:

test/test_routes.py

@@ -47,6 +47,11 @@ def test_ddg_bang(client):
     assert rv._status_code == 302
     assert rv.headers.get('Location').startswith('https://github.com')
 
+    # Ensure bang without content doesn't redirect to the result
+    rv = client.get(f'/{Endpoint.search}?q=!gh')
+    assert rv._status_code == 302
+    assert not rv.headers.get('Location').startswith('https://github.com')
+
 
 def test_config(client):
     rv = client.post(f'/{Endpoint.config}', data=demo_config)