Fix race condition causing failed Travis builds #75.3 and #81.1.

minecraft/networking/connection.py

@@ -184,15 +184,16 @@ class Connection(object):
         Attempt to begin connecting to the server.
         May safely be called multiple times after the first, i.e. to reconnect.
         """
-        self.spawned = False
         with self._write_lock:
+            # We hold the lock throughout, as connect() may be called by both
+            # the network thread and a parent thread simultaneously, during
+            # automatic version negotiation.
+
+            self.spawned = False
             self._outgoing_packet_queue = deque()
 
             self._connect()
             self._handshake()
-
-        self.reactor = LoginReactor(self)
-        self._start_network_thread()
             login_start_packet = packets.LoginStartPacket()
             if self.auth_token:
                 login_start_packet.name = self.auth_token.profile.name
@@ -200,6 +201,9 @@ class Connection(object):
                 login_start_packet.name = self.username
             self.write_packet(login_start_packet)
 
+            self.reactor = LoginReactor(self)
+            self._start_network_thread()
+
     def _connect(self):
         # Connect a socket to the server and create a file object from the
         # socket.