Code review comment for lp:~apw/launchpad/signing-add-kernel-module-signing

Ok I have pushed up and update to this branch which I hope will fix these concerns. This has all the formatting bits applied. I have also revamped the testing of command execution to be much simpler. Finally it adds some additional tests which seemed to be absent for Kmod signing.

In reviewing the command handling for testing I realised that the signing.py code had the call and emit error form repeated all over the place so I have pulled that out to its own helper, by doing this I now have a much more tractible test point for the unit-tests to hang off of. This has made the testing much simpler. I have also moved all tests that need keys made to the new form allowing removal of the duplicated FakeMethods for key generation.