attempt to handle exit signal cleanly

Author: sspickle

vpython/no_notebook.py

@@ -334,6 +334,7 @@ def stop_server():
     """Shuts down all threads and exits cleanly."""
     global __server
     __server.shutdown()
+
     event_loop = txaio.config.loop
     event_loop.stop()
     # We've told the event loop to stop, but it won't shut down until we poke
@@ -354,11 +355,11 @@ def stop_server():
     if threading.main_thread().is_alive():
         sys.exit(0)
     else:
-        pass
         # If the main thread has already stopped, the python interpreter
         # is likely just running .join on the two remaining threads (in
         # python/threading.py:_shutdown). Since we just stopped those threads,
         # we'll now exit.
+        sys.exit(0)  # but just in case....
 
 
 GW = GlowWidget()

vpython/vpython.py

@@ -16,14 +16,6 @@
 from ._vector_import_helper import (vector, mag, norm, cross, dot, adjust_up,
                                     adjust_axis, object_rotate)
 
-def Exit():
-    zero = 0.
-    print('exit')
-    a = 1.0/zero
-
-import atexit
-atexit.register(Exit)
-
 # List of names that will be imported from this file with import *
 __all__ = ['Camera', 'GlowWidget', 'version', 'GSversion', 'Mouse', 'arrow', 'attach_arrow',
            'attach_light', 'attach_trail', 'baseObj', 'box', 'bumpmaps', 'button',