Fixed the size limit tests in Python 3

- None cannot be compared to an integer in Python 3
- In Python 3 a request body must be bytes

bp python3

Change-Id: If3944f84d41f54089a8d245848c3012d566385f1
Fixed the policy tests in Python 3

The file builtin was removed in Python 3. open should be used instead.

bp python3

Change-Id: Ib394b9ceeffb1ae8fd4cbebbd0818c64e24e55e6
Adds several more tests to the Python 3 test run

bp python3

Change-Id: Idd1e60dff813a65898ce6a53d21a8d06fae2bdfe