Catch errors in history save thread, and print a briefer error message, rather than an ugly traceback.

IPython/core/history.py

@@ -486,6 +486,7 b' class HistorySavingThread(threading.Thread):'
         
     def run(self):
         # We need a separate db connection per thread:
+        try:
         self.db = sqlite3.connect(self.history_manager.hist_file)
         while True:
             self.history_manager.save_flag.wait()
@@ -493,6 +494,9 b' class HistorySavingThread(threading.Thread):'
                 return
             self.history_manager.save_flag.clear()
             self.history_manager.writeout_cache(self.db)
+        except Exception as e:
+            print(("The history saving thread hit an unexpected error (%s)."
+                   "History will not be written to the database.") % repr(e))
         
     def stop(self):
         """This can be called from the main thread to safely stop this thread.