Fix flake8 warning.
Fix undefined variable in release script
new tool: ravello-set-uuid
r-c-n: Fix specifying application by name
r-c-n: bugfix for --flavor pxe
r-c-n: fix for --network dhcp

By mistake we would not generate a Mac address for DHCP networks.
r-c-n: allow --network with --flavor pxe
Fix bug when login() is not explicitly called.