Changed to use _smuggle_referer

Removed `std_headers` import to satisfy flake8

youtube_dl/extractor/dropout.py

@@ -2,7 +2,7 @@
 from __future__ import unicode_literals
 
 from .common import InfoExtractor
-from .vimeo import VHXEmbedIE
+from .vimeo import VHXEmbedIE, VimeoIE
 from ..utils import (
     clean_html,
     ExtractorError,
@@ -11,8 +11,7 @@ from ..utils import (
     get_elements_by_class,
     int_or_none,
     unified_strdate,
-    urlencode_postdata,
-    std_headers
+    urlencode_postdata
 )
 
 
@@ -139,8 +138,6 @@ class DropoutIE(InfoExtractor):
             raise ExtractorError('Incorrect username/password')
 
     def _real_extract(self, url):
-        std_headers['Referer'] = 'https://www.dropout.tv'  # See issue 2858
-
         display_id = self._match_id(url)
         try:
             logged_in = self._login(display_id)
@@ -166,7 +163,7 @@ class DropoutIE(InfoExtractor):
         return {
             '_type': 'url_transparent',
             'ie_key': VHXEmbedIE.ie_key(),
-            'url': embed_url,
+            'url': VimeoIE._smuggle_referrer(embed_url, 'https://www.dropout.tv'),
             'id': self._search_regex(r'embed.vhx.tv/videos/(.+?)\?', embed_url, 'id'),
             'display_id': display_id,
             'title': title,

youtube_dl/extractor/vimeo.py

@@ -1146,8 +1146,15 @@ class VHXEmbedIE(VimeoBaseInfoExtractor):
         return unescapeHTML(mobj.group(1)) if mobj else None
 
     def _real_extract(self, url):
+        url, data = unsmuggle_url(url, {})
+        headers = std_headers.copy()
+        if 'http_headers' in data:
+            headers.update(data['http_headers'])
+        if 'Referer' not in headers:
+            headers['Referer'] = url
+
         video_id = self._match_id(url)
-        webpage = self._download_webpage(url, video_id)
+        webpage = self._download_webpage(url, video_id, headers=headers)
         config_url = self._parse_json(self._search_regex(
             r'window\.OTTData\s*=\s*({.+})', webpage,
             'ott data'), video_id, js_to_json)['config_url']