I have a similar issue to this: How can I skip Fabric connections that ask for a password? which has no answer. I\'m looking for a way to get Fabric to consider bad any host ask
I believe env.abort_on_prompts will achieve what you need, i.e. fail if there is a need for any kind of user interaction, while working when public key authentication is possible.
According to the documentation, this option calls abort() which in turn make use of sys.exit, which raises SystemExit making it possible to detect and recover from inner calls to abort by using except SystemExit or similar.
I just patched up the utils.py in fabric to return a raise instead of sys.exit(1). let's you handle it cleanly instead of it crapping itself.
(about line 34)
else:
#sys.exit(1)
raise("I broke")