[fix] tests

searx/engines/bing_images.py

 # search-url
 base_url = 'https://www.bing.com/'
 search_string = 'images/search?{query}&count=10&first={offset}'
-thumb_url = "http://ts1.mm.bing.net/th?id={ihk}" # no https, bad certificate
+thumb_url = "http://ts1.mm.bing.net/th?id={ihk}"  # no https, bad certificate
 
 # safesearch definitions
 safesearch_types = {2: 'STRICT',

searx/tests/engines/test_currency_convert.py

         self.assertEqual(len(results), 1)
         self.assertEqual(results[0]['answer'], '10 EUR = 5.0 USD (1 EUR = 0.5 USD)')
         now_date = datetime.now().strftime('%Y%m%d')
-        self.assertEqual(results[0]['url'], 'http://finance.yahoo.com/currency/converter-results/' +
+        self.assertEqual(results[0]['url'], 'https://finance.yahoo.com/currency/converter-results/' +
                                             now_date + '/10-eur-to-usd.html')

searx/tests/engines/test_stackoverflow.py

         self.assertEqual(type(results), list)
         self.assertEqual(len(results), 1)
         self.assertEqual(results[0]['title'], 'This is the title')
-        self.assertEqual(results[0]['url'], 'http://stackoverflow.com/questions/this.is.the.url')
+        self.assertEqual(results[0]['url'], 'https://stackoverflow.com/questions/this.is.the.url')
         self.assertEqual(results[0]['content'], 'This is the content')
 
         html = """

searx/tests/engines/test_vimeo.py

         self.assertEqual(type(results), list)
         self.assertEqual(len(results), 1)
         self.assertEqual(results[0]['title'], 'This is the title')
-        self.assertEqual(results[0]['url'], 'http://vimeo.com/videoid')
+        self.assertEqual(results[0]['url'], 'https://vimeo.com/videoid')
         self.assertEqual(results[0]['content'], '')
         self.assertEqual(results[0]['thumbnail'], 'http://image.url.webp')
         self.assertIn('/videoid', results[0]['embedded'])