Test that an object follows our Unicode policy. See
“Unicode guidelines” in the coding guidelines.
Parameters:
x : object
The instance to test
roundtrip : module, optional
When provided, this namespace will be used to evaluate
repr(x) and ensure that it roundtrips. It will also
ensure that __bytes__(x) and __unicode__(x) roundtrip.
If not provided, no roundtrip testing will be performed.