Add an extractor for common mistakes (#4610)

youtube_dl/extractor/__init__.py

@@ -71,6 +71,7 @@
 from .collegehumor import CollegeHumorIE
 from .comedycentral import ComedyCentralIE, ComedyCentralShowsIE
 from .comcarcoff import ComCarCoffIE
+from .commonmistakes import CommonMistakesIE
 from .condenast import CondeNastIE
 from .cracked import CrackedIE
 from .criterion import CriterionIE

youtube_dl/extractor/commonmistakes.py

@@ -0,0 +1,29 @@
+from __future__ import unicode_literals
+
+from .common import InfoExtractor
+from ..utils import ExtractorError
+
+
+class CommonMistakesIE(InfoExtractor):
+    IE_DESC = False  # Do not list
+    _VALID_URL = r'''(?x)
+        (?:url|URL)
+    '''
+
+    _TESTS = [{
+        'url': 'url',
+        'only_matching': True,
+    }, {
+        'url': 'URL',
+        'only_matching': True,
+    }]
+
+    def _real_extract(self, url):
+        msg = (
+            'You\'ve asked youtube-dl to download the URL "%s". '
+            'That doesn\'t make any sense. '
+            'Simply remove the parameter in your command or configuration.'
+        ) % url
+        if self._downloader.params.get('verbose'):
+            msg += ' Add -v to the command line to see what arguments and configuration youtube-dl got.'
+        raise ExtractorError(msg, expected=True)