[#2900] Fix Error loading torrent: invalid bencoded value

* Testing the torrent with other bencode libs doesn't raise exceptions
   so just revert the 'small fix' applied in b193d87499.
 * Add BTFailure exception so bdecode issue can be caught in deluge code.

deluge/bencode.py

@@ -15,6 +15,10 @@
 from types import DictType, IntType, ListType, LongType, StringType, TupleType
 
 
+class BTFailure(Exception):
+    pass
+
+
 def decode_int(x, f):
     f += 1
     newf = x.index('e', f)
@@ -71,9 +75,7 @@ def bdecode(x):
     try:
         r, l = decode_func[x[0]](x, 0)
     except (IndexError, KeyError, ValueError):
-        raise Exception("not a valid bencoded string")
-    if l != len(x):
-        raise Exception("invalid bencoded value (data after valid prefix)")
+        raise BTFailure("not a valid bencoded string")
 
     return r
 

deluge/ui/common.py

@@ -74,7 +74,7 @@ class TorrentInfo(object):
             with open(filename, "rb") as _file:
                 self.__m_filedata = _file.read()
             self.__m_metadata = bencode.bdecode(self.__m_filedata)
-        except Exception as ex:
+        except bencode.BTFailure as ex:
             log.warning("Unable to open %s: %s", filename, ex)
             raise ex