Revert "remove 'all' option from search languages"

This reverts commit 4d1770398a.

searx/search.py

@@ -24,7 +24,7 @@ from flask_babel import gettext
 import requests.exceptions
 import searx.poolrequests as requests_lib
 from searx.engines import (
-    categories, engines, settings
+    categories, engines
 )
 from searx.answerers import ask
 from searx.utils import gen_useragent
@@ -221,10 +221,6 @@ def get_search_query_from_webapp(preferences, form):
     else:
         query_lang = preferences.get_value('language')
 
-    # provides backwards compatibility for requests using old language default
-    if query_lang == 'all':
-        query_lang = settings['search']['language']
-
     # check language
     if not VALID_LANGUAGE_CODE.match(query_lang):
         raise SearxParameterException('language', query_lang)