dulwich does not handle repository urls without a protocol (i.e. <email address hidden>)

[Adam Plumb]

If I try to clone a repository from github using the dulwich bin client and a read+write url they provide for each repository I get the following exception:

   1.
      $ ./dulwich clone <email address hidden>:adamplumb/PhotoRate.git /home/adam/Development/PhotoRate
   2.
      fatal: '<email address hidden>:adamplumb/PhotoRate.git' does not appear to be a git repository
   3.
      Traceback (most recent call last):
   4.
        File "./dulwich", line 186, in <module>
   5.
          commands[cmd](sys.argv[2:])
   6.
        File "./dulwich", line 153, in cmd_clone
   7.
          progress=sys.stdout.write)
   8.
        File "/home/adam/Development/python/dulwich/client.py", line 150, in fetch
   9.
          target.get_graph_walker(), f.write, progress)
  10.
        File "/home/adam/Development/python/dulwich/client.py", line 284, in fetch_pack
  11.
          progress)
  12.
        File "/home/adam/Development/python/dulwich/client.py", line 163, in fetch_pack
  13.
          (refs, server_capabilities) = self.read_refs()
  14.
        File "/home/adam/Development/python/dulwich/client.py", line 82, in read_refs
  15.
          for pkt in self.proto.read_pkt_seq():
  16.
        File "/home/adam/Development/python/dulwich/protocol.py", line 85, in read_pkt_seq
  17.
          pkt = self.read_pkt_line()
  18.
        File "/home/adam/Development/python/dulwich/protocol.py", line 72, in read_pkt_line
  19.
          raise HangupException()
  20.
      dulwich.errors.HangupException: The remote server unexpectedly closed the connection.

This is a git+ssh protocol in disguise.