Add --socks-proxy parameter to use SOCKS proxy

This allows the user to specify a socks proxy to
tunnel the connection through. This feature requires that
PySocks is available. If the user tries to use a SOCKS proxy
without PySocks available an error is printed and the process is
aborted.

youtube_dl/YoutubeDL.py

@@ -52,6 +52,7 @@ from .utils import (
     locked_file,
     make_HTTPS_handler,
     MaxDownloadsReached,
+    OptionalDependencyNotFound,
     PagedList,
     parse_filesize,
     PerRequestProxyHandler,
@@ -1953,11 +1954,39 @@ class YoutubeDL(object):
                 proxies['https'] = proxies['http']
         proxy_handler = PerRequestProxyHandler(proxies)
 
+        socks_handler = None
+        opts_socks = self.params.get('socksproxy')
+        if opts_socks is not None and opts_socks:
+            # Try to import the dependencies for this feature
+            try:
+                import socks
+            except ImportError:
+                raise OptionalDependencyNotFound(module_name='socks',
+                                                 feature_name='--socks-proxy')
+            try:
+                from sockshandler import SocksiPyHandler
+            except ImportError:
+                raise OptionalDependencyNotFound(module_name='sockshandler',
+                                                 feature_name='--socks-proxy')
+
+            pair = opts_socks.split(':')
+            if len(pair) == 2:
+                socks_handler = SocksiPyHandler(socks.PROXY_TYPE_SOCKS5,
+                                                pair[0],
+                                                int(pair[1]))
+            else:
+                socks_handler = SocksiPyHandler(socks.PROXY_TYPE_SOCKS5,
+                                                'localhost',
+                                                int(pair[0]))
+
         debuglevel = 1 if self.params.get('debug_printtraffic') else 0
         https_handler = make_HTTPS_handler(self.params, debuglevel=debuglevel)
         ydlh = YoutubeDLHandler(self.params, debuglevel=debuglevel)
-        opener = compat_urllib_request.build_opener(
-            proxy_handler, https_handler, cookie_processor, ydlh)
+        proxy_list = []
+        if socks_handler:
+            proxy_list.append(socks_handler)
+        proxy_list += [proxy_handler, https_handler, cookie_processor, ydlh]
+        opener = compat_urllib_request.build_opener(*proxy_list)
 
         # Delete the default user-agent header, which would otherwise apply in
         # cases where our custom HTTP handler doesn't come into play

youtube_dl/__init__.py

@@ -29,6 +29,7 @@ from .utils import (
     DownloadError,
     match_filter_func,
     MaxDownloadsReached,
+    OptionalDependencyNotFound,
     preferredencoding,
     read_batch_urls,
     SameFileError,
@@ -346,6 +347,7 @@ def _real_main(argv=None):
         'nocheckcertificate': opts.no_check_certificate,
         'prefer_insecure': opts.prefer_insecure,
         'proxy': opts.proxy,
+        'socksproxy': opts.socksproxy,
         'socket_timeout': opts.socket_timeout,
         'bidi_workaround': opts.bidi_workaround,
         'debug_printtraffic': opts.debug_printtraffic,
@@ -414,5 +416,7 @@ def main(argv=None):
         sys.exit('ERROR: fixed output name but more than one file to download')
     except KeyboardInterrupt:
         sys.exit('\nERROR: Interrupted by user')
+    except OptionalDependencyNotFound as e:
+        sys.exit(str(e))
 
 __all__ = ['main', 'YoutubeDL', 'gen_extractors', 'list_extractors']

youtube_dl/options.py

@@ -181,6 +181,11 @@ def parseOpts(overrideArguments=None):
         '--proxy', dest='proxy',
         default=None, metavar='URL',
         help='Use the specified HTTP/HTTPS proxy. Pass in an empty string (--proxy "") for direct connection')
+    network.add_option(
+        '--socks-proxy', dest='socksproxy', default=None, metavar='URL',
+        help=('Use the specified socks proxy. Pass in an empty string '
+              '(--socks-proxy "") for direct connection. This feature requires'
+              'the pysocks library.'))
     network.add_option(
         '--socket-timeout',
         dest='socket_timeout', type=float, default=None, metavar='SECONDS',

youtube_dl/utils.py

@@ -586,6 +586,23 @@ class ContentTooShortError(Exception):
         self.expected = expected
 
 
+class OptionalDependencyNotFound(Exception):
+    """Optional dependency not found
+
+    This exception may be raised by YoutubeDL, when the user tries to use a
+    feature that requires an optional dependency which could not be found.
+    """
+
+    def __init__(self, module_name, feature_name):
+        self.module_name = str(module_name)
+        self.feature_name = str(feature_name)
+
+    def __str__(self):
+        return ("Unable to use '{feature}', because it depends on '{module}' "
+                "which was not found.").format(
+            feature=self.feature_name, module=self.module_name)
+
+
 def _create_http_connection(ydl_handler, http_class, is_https, *args, **kwargs):
     # Working around python 2 bug (see http://bugs.python.org/issue17849) by limiting
     # expected HTTP responses to meet HTTP/1.0 or later (see also