Fix imports and general cleanup

· Import from compat what comes from compat. Yes, some names are available in utils too, but that's an implementation detail.
· Use _match_id consistently whenever possible
· Fix some outdated tests
· Use consistent valid URL (always match the whole protocol, no ^ at start required)
· Use modern test definitions

youtube_dl/extractor/playvid.py

@@ -3,31 +3,31 @@ from __future__ import unicode_literals
 import re
 
 from .common import InfoExtractor
-from ..utils import (
-    ExtractorError,
-    clean_html,
+from ..compat import (
     compat_urllib_parse,
 )
+from ..utils import (
+    clean_html,
+    ExtractorError,
+)
 
 
 class PlayvidIE(InfoExtractor):
-    _VALID_URL = r'^https?://www\.playvid\.com/watch(\?v=|/)(?P<id>.+?)(?:#|$)'
+    _VALID_URL = r'https?://www\.playvid\.com/watch(\?v=|/)(?P<id>.+?)(?:#|$)'
     _TEST = {
-        'url': 'http://www.playvid.com/watch/agbDDi7WZTV',
-        'md5': '44930f8afa616efdf9482daf4fe53e1e',
+        'url': 'http://www.playvid.com/watch/RnmBNgtrrJu',
+        'md5': 'ffa2f6b2119af359f544388d8c01eb6c',
         'info_dict': {
-            'id': 'agbDDi7WZTV',
+            'id': 'RnmBNgtrrJu',
             'ext': 'mp4',
-            'title': 'Michelle Lewin in Miami Beach',
-            'duration': 240,
+            'title': 'md5:9256d01c6317e3f703848b5906880dc8',
+            'duration': 82,
             'age_limit': 18,
         }
     }
 
     def _real_extract(self, url):
-        mobj = re.match(self._VALID_URL, url)
-        video_id = mobj.group('id')
-
+        video_id = self._match_id(url)
         webpage = self._download_webpage(url, video_id)
 
         m_error = re.search(