5 files changed, 7 insertions, 3 deletions
diff --git a/youtube_dl/extractor/bokecc.py b/youtube_dl/extractor/bokecc.py
index 6017e8344..4b8bef391 100644
--- a/youtube_dl/extractor/bokecc.py
+++ b/youtube_dl/extractor/bokecc.py
@@ -32,7 +32,7 @@ class BokeCCBaseIE(InfoExtractor):
 
 
 class BokeCCIE(BokeCCBaseIE):
-    _IE_DESC = 'CC视频'
+    IE_DESC = 'CC视频'
     _VALID_URL = r'https?://union\.bokecc\.com/playvideo\.bo\?(?P<query>.*)'
 
     _TESTS = [{
diff --git a/youtube_dl/extractor/cloudy.py b/youtube_dl/extractor/cloudy.py
index 85ca20ecc..d39a9a5c2 100644
--- a/youtube_dl/extractor/cloudy.py
+++ b/youtube_dl/extractor/cloudy.py
@@ -9,7 +9,7 @@ from ..utils import (
 
 
 class CloudyIE(InfoExtractor):
-    _IE_DESC = 'cloudy.ec'
+    IE_DESC = 'cloudy.ec'
     _VALID_URL = r'https?://(?:www\.)?cloudy\.ec/(?:v/|embed\.php\?.*?\bid=)(?P<id>[A-Za-z0-9]+)'
     _TESTS = [{
         'url': 'https://www.cloudy.ec/v/af511e2527aac',
diff --git a/youtube_dl/extractor/common.py b/youtube_dl/extractor/common.py
index 78704b557..cb67b976d 100644
--- a/youtube_dl/extractor/common.py
+++ b/youtube_dl/extractor/common.py
@@ -422,6 +422,8 @@ class InfoExtractor(object):
     _GEO_COUNTRIES = None
     _GEO_IP_BLOCKS = None
     _WORKING = True
+    # supply this in public subclasses: used in supported sites list, etc
+    # IE_DESC = 'short description of IE'
 
     def __init__(self, downloader=None):
         """Constructor. Receives an optional downloader."""
diff --git a/youtube_dl/extractor/senateisvp.py b/youtube_dl/extractor/senateisvp.py
index db5ef8b57..b8ac58713 100644
--- a/youtube_dl/extractor/senateisvp.py
+++ b/youtube_dl/extractor/senateisvp.py
@@ -47,7 +47,7 @@ class SenateISVPIE(InfoExtractor):
         ['vetaff', '76462', 'http://vetaff-f.akamaihd.net'],
         ['arch', '', 'http://ussenate-f.akamaihd.net/']
     ]
-    _IE_NAME = 'senate.gov'
+    IE_NAME = 'senate.gov'
     _VALID_URL = r'https?://(?:www\.)?senate\.gov/isvp/?\?(?P<qs>.+)'
     _TESTS = [{
         'url': 'http://www.senate.gov/isvp/?comm=judiciary&type=live&stt=&filename=judiciary031715&auto_play=false&wmode=transparent&poster=http%3A%2F%2Fwww.judiciary.senate.gov%2Fthemes%2Fjudiciary%2Fimages%2Fvideo-poster-flash-fit.png',
diff --git a/youtube_dl/jsinterp.py b/youtube_dl/jsinterp.py
index f0c4fa928..69c8f77ca 100644
--- a/youtube_dl/jsinterp.py
+++ b/youtube_dl/jsinterp.py
@@ -686,6 +686,8 @@ class JSInterpreter(object):
             raise self.Exception('Cannot get index {idx!r:.100}'.format(**locals()), expr=repr(obj), cause=e)
 
     def _dump(self, obj, namespace):
+        if obj is JS_Undefined:
+            return 'undefined'
         try:
             return json.dumps(obj)
         except TypeError: