make OSErrors during file downloads nonfatal (closes #512)

… except ENOSPC (No space left on device), since there is no reason to
continue downloading in that case.

All other errors that would prevent downloading data and writing it to
disk get already raised during directory creation and are therefore not
checked here.

gallery_dl/job.py

@@ -8,6 +8,7 @@
 
 import sys
 import time
+import errno
 import logging
 from . import extractor, downloader, postprocessor
 from . import config, text, util, output, exception
@@ -292,7 +293,13 @@ def download(self, url):
         scheme = url.partition(":")[0]
         downloader = self.get_downloader(scheme)
         if downloader:
-            return downloader.download(url, self.pathfmt)
+            try:
+                return downloader.download(url, self.pathfmt)
+            except OSError as exc:
+                if exc.errno == errno.ENOSPC:
+                    raise
+                self.log.warning("%s: %s", exc.__class__.__name__, exc)
+                return False
         self._write_unsupported(url)
         return False