Remove mox3 requirement

mox3 is only used got py3 testing when converting tests from mox,
all OSC tests are new so we don't need it.

Change-Id: I2fae539e99143f91048c95d1e46cfbd7b0e9bdb0
Release notes for 0.3.0 release

Change-Id: I6f025b745378613eb674e13dd503e57d049a3e50