[tests] don't fail on network errors

This is suboptimal, but at least this way we will need to look at the logs
only to check for network errors that happen too often, instead of
parsing a ton of lines each time to see if there is some true test failing

test/helper.py

@@ -5,9 +5,11 @@ import json
 import os.path
 import re
 import types
+import sys
 
 import youtube_dl.extractor
 from youtube_dl import YoutubeDL
+from youtube_dl.utils import preferredencoding
 
 
 def global_setup():
@@ -33,6 +35,21 @@ def try_rm(filename):
             raise
 
 
+def report_warning(message):
+    '''
+    Print the message to stderr, it will be prefixed with 'WARNING:'
+    If stderr is a tty file the 'WARNING:' will be colored
+    '''
+    if sys.stderr.isatty() and os.name != 'nt':
+        _msg_header = u'\033[0;33mWARNING:\033[0m'
+    else:
+        _msg_header = u'WARNING:'
+    output = u'%s %s\n' % (_msg_header, message)
+    if 'b' in getattr(sys.stderr, 'mode', '') or sys.version_info[0] < 3:
+        output = output.encode(preferredencoding())
+    sys.stderr.write(output)
+
+
 class FakeYDL(YoutubeDL):
     def __init__(self, override=None):
         # Different instances of the downloader can't share the same dictionary