Chapter 7 Python dynamic inventory example needs two fixes for Python 3

[geerlingguy]

This line is particularly incompatible with Python 3:

print json.dumps(self.inventory);

Not only is there a semicolon (egads!!!), it needs to use the new Python 3-style print statement:

print(json.dumps(self.inventory))

[geerlingguy]

Also set the hashbang to:

#!/usr/bin/env python3

[geerlingguy]

This will be in the next version of the book.