suite.TestRunCmd shows script failure

This is an example

FAIL: plugin_test.go:158: suite.TestRunCmd

plugin_test.go:168:
    c.Assert(strings.TrimSpace(string(out)), gc.DeepEquals, m.stdout)
... obtained string = "" +
... "c:\\users\\admini~1\\appdata\\local\\temp\\tmpddmpf8\\gogo\\src\\github.com\\juju\\juju\\process\\plugin>echo ! (int=0) 1>&2 \r\n" +
... "\r\n" +
... "c:\\users\\admini~1\\appdata\\local\\temp\\tmpddmpf8\\gogo\\src\\github.com\\juju\\juju\\process\\plugin>echo \"!s(MISSING)\" \r\n" +
... "\"!s(MISSING)\"\r\n" +
... "\r\n" +
... "c:\\users\\admini~1\\appdata\\local\\temp\\tmpddmpf8\\gogo\\src\\github.com\\juju\\juju\\process\\plugin>exit !d(MISSING)"
... expected string = "foo!"

----------------------------------------------------------------------
FAIL: plugin_test.go:173: suite.TestRunCmdErr

plugin_test.go:183:
    c.Assert(err, gc.ErrorMatches, "exit status 1: foo!")
... value = nil
... regex string = "exit status 1: foo!"
... Error value is nil

This is because I was doing stupid scripting tricks to try to have a usable executable to test. I've swapped out that code with much more reliable code that uses the testing executable as the executable to run, which means all the code is written in Go and cross platform compatible.

PR for this bug here: https://github.com/juju/juju/pull/2795
Review here: http://reviews.vapour.ws/r/2174/

CI will fail the Feature Proc management
    http://reports.vapour.ws/releases/2919
 soon because of

----------------------------------------------------------------------
FAIL: plugin_test.go:163: suite.TestRunCmd

plugin_test.go:172:
    c.Assert(err, jc.ErrorIsNil)
... value *errors.Err = &errors.Err{message:"", cause:(*exec.ExitError)(0xc0840a8d30), previous:(*exec.ExitError)(0xc0840a8d30), file:"github.com/juju/juju/process/plugin/plugin.go", line:152} ("exit status 2")
... error stack:
 exit status 2
 github.com/juju/juju/process/plugin/plugin.go:152:

----------------------------------------------------------------------
FAIL: plugin_test.go:178: suite.TestRunCmdErr

plugin_test.go:187:
    c.Assert(err, gc.ErrorMatches, "exit status 1: foo!")
... error string = "exit status 2"
... regex string = "exit status 1: foo!"

OOPS: 9 passed, 2 FAILED
--- FAIL: Test (0.08 seconds)
FAIL
FAIL github.com/juju/juju/process/plugin 0.388s

The predicted location of the log is:
    http://reports.vapour.ws/releases/2919/job/run-unit-tests-win2012-amd64/attempt/976