Context Navigation

Changes between Initial Version and Version 1 of Ticket #2023, comment 16

initial	v1
1		Daira and I decided that it'd be slightly easier to fix this by dodging the bug: modify iputil.py (and other code that uses subprocess) to check for the existence of the executable before allowing `subprocess.Popen` to try and run it. This seems to work, and avoids adding a new dependency. I'll file a PR with this change in a moment. Hopefully this will tide us over until 1.11 is released, and we can switch to a whole new way of managing local IP addresses (probably by having the Introducer tell us, or requiring server admins to configure them explicitly).
	1	Daira and I decided that it'd be slightly easier to fix this by dodging the bug: modify iputil.py (and other code that uses subprocess) to check for the existence of the executable before allowing `subprocess.Popen` to try and run it. This seems to work, and avoids adding a new dependency. I'll file a PR with this change in a moment. Hopefully this will tide us over until 1.11 is released, and we can switch to a whole new way of managing local IP addresses (probably by having the Introducer tell us ala #50 or #2152, or requiring server admins to configure them explicitly).