Don't fight gnuflag; make use of its --help feature

cmd/context_test.go

 package cmd_test
 
 import (
         "bytes"
         "errors"
         "io"
         "io/ioutil"
         "launchpad.net/gnuflag"
         . "launchpad.net/gocheck"
         cmd "launchpad.net/juju/go/cmd"
@@ skipping 51 matching lines @@
 cmd-doc
 `
 
 type ContextSuite struct{}
 
 func AssertMainOutput(c *C, com cmd.Command, usage string) {
         ctx := dummyContext(c)
         result := cmd.Main(com, ctx, []string{"--unknown"})
         c.Assert(result, Equals, 2)
         c.Assert(str(ctx.Stdout), Equals, "")
-        expected := "ERROR: flag provided but not defined: --unknown\n" + usage
+        expected := usage + "error: flag provided but not defined: --unknown\n"
         c.Assert(str(ctx.Stderr), Equals, expected)
 }
 
 func (s *CommandSuite) TestMainOutput(c *C) {
         AssertMainOutput(c, &CtxCommand{}, fullUsage)
         AssertMainOutput(c, &CtxCommand{Minimal: true}, minUsage)
 }
 
 func (s *CommandSuite) TestMainBadRun(c *C) {
         ctx := dummyContext(c)
         result := cmd.Main(&CtxCommand{}, ctx, []string{"--opt", "error"})
         c.Assert(result, Equals, 1)
         c.Assert(str(ctx.Stdout), Equals, "")
-        c.Assert(str(ctx.Stderr), Equals, "ERROR: oh noes!\n")
+        c.Assert(str(ctx.Stderr), Equals, "error: oh noes!\n")
 }
 
 func (s *CommandSuite) TestMainSuccess(c *C) {
         ctx := dummyContext(c)
         result := cmd.Main(&CtxCommand{}, ctx, []string{"--opt", "success!"})
         c.Assert(result, Equals, 0)
         c.Assert(str(ctx.Stdout), Equals, "hello stdout: success!")
         c.Assert(str(ctx.Stderr), Equals, "hello stderr: success!")
 }
 
@@ skipping 45 matching lines @@
 func (s *CommandSuite) TestRelativeLogFile(c *C) {
         defer saveLog()()
         ctx := dummyContext(c)
         err := ctx.InitLog(false, false, "logfile")
         c.Assert(err, IsNil)
         log.Printf("hello log")
         raw, err := ioutil.ReadFile(filepath.Join(ctx.Dir, "logfile"))
         c.Assert(err, IsNil)
         c.Assert(string(raw), Matches, ".* JUJU hello log\n")
 }