display if an engine does not support https

Closes #302

searx/engines/__init__.py

@@ -20,6 +20,7 @@ import sys
 import threading
 from os.path import realpath, dirname
 from babel.localedata import locale_identifiers
+from urllib.parse import urlparse
 from flask_babel import gettext
 from operator import itemgetter
 from searx import settings
@@ -289,3 +290,34 @@ def initialize_engines(engine_list):
             if init_fn:
                 logger.debug('%s engine: Starting background initialization', engine_name)
                 threading.Thread(target=engine_init, args=(engine_name, init_fn)).start()
+
+        _set_https_support_for_engine(engine)
+
+
+def _set_https_support_for_engine(engine):
+    # check HTTPS support if it is not disabled
+    if not engine.offline and not hasattr(engine, 'https_support'):
+        params = engine.request('http_test', {
+            'method': 'GET',
+            'headers': {},
+            'data': {},
+            'url': '',
+            'cookies': {},
+            'verify': True,
+            'auth': None,
+            'pageno': 1,
+            'time_range': None,
+            'language': '',
+            'safesearch': False,
+            'is_test': True,
+            'category': 'files',
+            'raise_for_status': True,
+        })
+
+        if 'url' not in params:
+            return
+
+        parsed_url = urlparse(params['url'])
+        https_support = parsed_url.scheme == 'https'
+
+        setattr(engine, 'https_support', https_support)