Add new types of exception.

p2pfs/core/exceptions.py

@@ -1,3 +1,17 @@
 class DownloadIncompleteError(EOFError):
-    def __init__(self, chunknum):
+    def __init__(self, message, chunknum):
+        super().__init__(message)
         self.chunknum = chunknum
+
+
+class AlreadyConnectedError(ConnectionError):
+    def __init__(self, address):
+        self.address = address
+
+
+class TrackerNotConnectedError(ConnectionError):
+    pass
+
+
+class InProgressError(Exception):
+    pass