Add support for single-test tox runs

Use a sintax like
    tox test.test_download:TestDownload.test_NowVideo
to run the specific test on all the tox environments (Python versions)

test/test_age_restriction.py

@@ -8,7 +8,7 @@ import os
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 from youtube_dl import YoutubeDL
-from helper import try_rm
+from .helper import try_rm
 
 
 def _download_restricted(url, filename, age):

test/test_all_urls.py

@@ -8,7 +8,7 @@ import os
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 from youtube_dl.extractor import YoutubeIE, YoutubePlaylistIE, YoutubeChannelIE, JustinTVIE, gen_extractors
-from helper import get_testcases
+from .helper import get_testcases
 
 class TestAllURLsMatching(unittest.TestCase):
     def setUp(self):

test/test_dailymotion_subtitles.py

@@ -10,7 +10,7 @@ sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 from youtube_dl.extractor import DailymotionIE
 from youtube_dl.utils import *
-from helper import FakeYDL
+from .helper import FakeYDL
 
 md5 = lambda s: hashlib.md5(s.encode('utf-8')).hexdigest()
 

test/test_download.py

@@ -37,8 +37,8 @@ def _file_md5(fn):
     with open(fn, 'rb') as f:
         return hashlib.md5(f.read()).hexdigest()
 
-import helper  # Set up remaining global configuration
-from helper import get_testcases, try_rm
+import test.helper as helper  # Set up remaining global configuration
+from .helper import get_testcases, try_rm
 defs = get_testcases()
 
 with io.open(PARAMETERS_FILE, encoding='utf-8') as pf:

test/test_playlists.py

@@ -20,7 +20,7 @@ from youtube_dl.extractor import (
 )
 from youtube_dl.utils import *
 
-from helper import FakeYDL
+from .helper import FakeYDL
 
 class TestPlaylists(unittest.TestCase):
     def assertIsPlaylist(self, info):

test/test_youtube_lists.py

@@ -11,7 +11,7 @@ sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from youtube_dl.extractor import YoutubeUserIE, YoutubePlaylistIE, YoutubeIE, YoutubeChannelIE, YoutubeShowIE
 from youtube_dl.utils import *
 
-from helper import FakeYDL
+from .helper import FakeYDL
 
 class TestYoutubeLists(unittest.TestCase):
     def assertIsPlaylist(self,info):

test/test_youtube_subtitles.py

@@ -10,7 +10,7 @@ sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 from youtube_dl.extractor import YoutubeIE
 from youtube_dl.utils import *
-from helper import FakeYDL
+from .helper import FakeYDL
 
 md5 = lambda s: hashlib.md5(s.encode('utf-8')).hexdigest()
 

tox.ini

@@ -1,5 +1,8 @@
 [tox]
 envlist = py26,py27,py33
 [testenv]
-deps = nose
-commands = nosetests --with-coverage --cover-package=youtube_dl --cover-html --verbose test
+deps =
+   nose
+   coverage
+commands = nosetests --verbose {posargs:test}  # --with-coverage --cover-package=youtube_dl --cover-html
+                                               # test.test_download:TestDownload.test_NowVideo