Improve geo bypass mechanism

* Rename options to preffixly match with --geo-verification-proxy
* Introduce _GEO_COUNTRIES for extractors
* Implement faking IP right away for sites with known geo restriction

youtube_dl/extractor/ondemandkorea.py

@@ -10,6 +10,7 @@ from ..utils import (
 
 class OnDemandKoreaIE(InfoExtractor):
     _VALID_URL = r'https?://(?:www\.)?ondemandkorea\.com/(?P<id>[^/]+)\.html'
+    _GEO_COUNTRIES = ['US', 'CA']
     _TEST = {
         'url': 'http://www.ondemandkorea.com/ask-us-anything-e43.html',
         'info_dict': {
@@ -36,7 +37,7 @@ class OnDemandKoreaIE(InfoExtractor):
         if 'msg_block_01.png' in webpage:
             self.raise_geo_restricted(
                 msg='This content is not available in your region',
-                countries=['US', 'CA'])
+                countries=self._GEO_COUNTRIES)
 
         if 'This video is only available to ODK PLUS members.' in webpage:
             raise ExtractorError(