log to file from publisher

also fix sd_hash exception that could happen

lbrynet/lbryfilemanager/LBRYFileDownloader.py

@@ -33,7 +33,8 @@ class ManagedLBRYFileDownloader(LBRYFileSaver):
         d = self.stream_info_manager._get_sd_blob_hashes_for_stream(self.stream_hash)
 
         def _save_sd_hash(sd_hash):
-            self.sd_hash = sd_hash[0]
+            if len(sd_hash):
+                self.sd_hash = sd_hash[0]
             return defer.succeed(None)
 
         d.addCallback(_save_sd_hash)

lbrynet/lbrynet_daemon/LBRYPublisher.py

@@ -1,15 +1,30 @@
+import logging
+import os
+import sys
+
+from appdirs import user_data_dir
+from datetime import datetime
+
 from lbrynet.core.Error import InsufficientFundsError
 from lbrynet.lbryfilemanager.LBRYFileCreator import create_lbry_file
 from lbrynet.lbryfile.StreamDescriptor import publish_sd_blob
 from lbrynet.core.PaymentRateManager import PaymentRateManager
 from lbrynet.lbryfilemanager.LBRYFileDownloader import ManagedLBRYFileDownloader
 from twisted.internet import threads, defer
-import os
-import logging
-from datetime import datetime
 
+if sys.platform != "darwin":
+    log_dir = os.path.join(os.path.expanduser("~"), ".lbrynet")
+else:
+    log_dir = user_data_dir("LBRY")
 
+if not os.path.isdir(log_dir):
+    os.mkdir(log_dir)
+
+LOG_FILENAME = os.path.join(log_dir, 'lbrynet-daemon.log')
 log = logging.getLogger(__name__)
+handler = logging.handlers.RotatingFileHandler(LOG_FILENAME, maxBytes=2097152, backupCount=5)
+log.addHandler(handler)
+log.setLevel(logging.INFO)
 
 
 class Publisher(object):