init_headers in daemon thread, and fix #1996

lib/blockchain.py

@@ -112,7 +112,8 @@ class Blockchain(util.PrintError):
             import urllib, socket
             socket.setdefaulttimeout(30)
             self.print_error("downloading ", self.headers_url)
-            urllib.urlretrieve(self.headers_url, filename)
+            urllib.urlretrieve(self.headers_url, filename + '.tmp')
+            os.rename(filename + '.tmp', filename)
             self.print_error("done.")
         except Exception:
             self.print_error("download failed. creating file", filename)

lib/network.py

@@ -813,7 +813,12 @@ class Network(util.DaemonThread):
             self.process_responses(interface)
 
     def run(self):
-        self.blockchain.init()
+        import threading
+        t = threading.Thread(target = self.blockchain.init)
+        t.daemon = True
+        t.start()
+        while t.isAlive() and self.is_running():
+            t.join(1)
         while self.is_running():
             self.maintain_sockets()
             self.wait_on_sockets()