Fix typos (#21901)

youtube_dl/extractor/leeco.py

@@ -326,7 +326,7 @@ class LetvCloudIE(InfoExtractor):
             elif play_json.get('code'):
                 raise ExtractorError('Letv cloud returned error %d' % play_json['code'], expected=True)
             else:
-                raise ExtractorError('Letv cloud returned an unknwon error')
+                raise ExtractorError('Letv cloud returned an unknown error')
 
         def b64decode(s):
             return compat_b64decode(s).decode('utf-8')

youtube_dl/extractor/rtlnl.py

@@ -32,7 +32,7 @@ class RtlNlIE(InfoExtractor):
             'duration': 1167.96,
         },
     }, {
-        # best format avaialble a3t
+        # best format available a3t
         'url': 'http://www.rtl.nl/system/videoplayer/derden/rtlnieuws/video_embed.html#uuid=84ae5571-ac25-4225-ae0c-ef8d9efb2aed/autoplay=false',
         'md5': 'dea7474214af1271d91ef332fb8be7ea',
         'info_dict': {

youtube_dl/extractor/soundcloud.py

@@ -197,7 +197,7 @@ class SoundcloudIE(InfoExtractor):
                 'skip_download': True,
             },
         },
-        # not avaialble via api.soundcloud.com/i1/tracks/id/streams
+        # not available via api.soundcloud.com/i1/tracks/id/streams
         {
             'url': 'https://soundcloud.com/giovannisarani/mezzo-valzer',
             'md5': 'e22aecd2bc88e0e4e432d7dcc0a1abf7',