Salts are generated poorly
generates the default salt once, at module import time. It will not change again until the module's imported. This means that someone using this who does not override the default will have the same salt for all passwords generated until a server restart. This defeats the purpose of having a salt.
The default value should probably be a callable, evaluated by the function at call time.
I don't think it's a huge issue that the salts are guessable, but there are much better functions to use for such a value, such as os.urandom().