The path behavior for rbt post was broken in a couple ways, probably for quite

some time. The first issue was that we had changed the `p4 change` usage to use

marshalled results, but the run_p4 method didn't respect the ignore_errors flag

when marshalling, and would call die(). Once I fixed this, the code that checks

the status of the changelist couldn't cope with error states. With these fixes,

_get_changelist_status will return None, which will cause parse_revision_spec

to correctly determine that the given path is not actually a revision.

Ran unit tests.