pep8 blank lines fixes

flake8 --select W391,E302,E301,E304

autopep8 can't fix W391 even though it claims it can.
Fixed using a simple custom script.

weboob/capabilities/torrent.py

@@ -29,6 +29,7 @@ class MagnetOnly(UserError):
     """
     Raised when trying to get URL to torrent but only magnet is available.
     """
+
     def __init__(self, magnet):
         self.magnet = magnet
         UserError.__init__(self, 'Only magnet URL is available')
@@ -58,6 +59,7 @@ class CapTorrent(Capability):
     """
     Torrent trackers.
     """
+
     def iter_torrents(self, pattern):
         """
         Search torrents and iterate on results.