Add an extractor for cmt.com (closes #2049)

It just inherits from MTVIE.
Some videos also come from vevo.com

youtube_dl/extractor/__init__.py

@@ -28,6 +28,7 @@
 from .cinemassacre import CinemassacreIE
 from .clipfish import ClipfishIE
 from .clipsyndicate import ClipsyndicateIE
+from .cmt import CMTIE
 from .cnn import CNNIE
 from .collegehumor import CollegeHumorIE
 from .comedycentral import ComedyCentralIE, ComedyCentralShowsIE

youtube_dl/extractor/cmt.py

@@ -0,0 +1,19 @@
+from .mtv import MTVIE
+
+class CMTIE(MTVIE):
+    IE_NAME = u'cmt.com'
+    _VALID_URL = r'https?://www\.cmt\.com/videos/.+?/(?P<videoid>[^/]+)\.jhtml'
+    _FEED_URL = 'http://www.cmt.com/sitewide/apps/player/embed/rss/'
+
+    _TESTS = [
+        {
+            u'url': u'http://www.cmt.com/videos/garth-brooks/989124/the-call-featuring-trisha-yearwood.jhtml#artist=30061',
+            u'md5': u'e6b7ef3c4c45bbfae88061799bbba6c2',
+            u'info_dict': {
+                u'id': u'989124',
+                u'ext': u'mp4',
+                u'title': u'Garth Brooks - "The Call (featuring Trisha Yearwood)"',
+                u'description': u'Blame It All On My Roots',
+            },
+        },
+    ]

youtube_dl/extractor/mtv.py

@@ -129,7 +129,7 @@ def _get_thumbnail_url(self, uri, itemdoc):
     def _real_extract(self, url):
         mobj = re.match(self._VALID_URL, url)
         video_id = mobj.group('videoid')
-        uri = mobj.group('mgid')
+        uri = mobj.groupdict().get('mgid')
         if uri is None:
             webpage = self._download_webpage(url, video_id)