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Connecting requires deleting and recreating the connection without routes - if
I add routes in the NM interface connecting the VPN [PPTP] fails, without
routes [adding them later with ip route...] works.  

It is not possible to delete the last route in a VPN connection once routes
have been added.  So the connection must be deleted and recreated to get rid of
all routes.

Deleting the connection crashes the NM control panel UI, it then needs to be
restarted so the connection can be recreated.

Reproducible: Always

Steps to Reproduce:
1. Create VPN connection
2. Add routes to VPN connection
3. Fails to connect
Actual Results:  
Fails to connect, with no helpful user presented error message.

Expected Results:  
Connect, with routes inserted to routing tables; as it has worked for years.