Fix action argument for the --no-fake option.
Change the help message for migration subcommand to make the subcommand easier to use.
Fix PEP 8 line length violation
Add test case for --no-fake switch

This test case is not a proper test for the fix, however.  To actually test
the fix, we would have to use a shell command instead of the internal API,
which would necessitate converting TransactionTestCase to TestCase, which
would hose many of the test methods in BackupTestCase.
Merge pull request #173 from murphyke/kev-2.2-171

Fix action argument for the --no-fake option