Much better, thanks! LGTM with just a few formatting suggestions below.
Make sure you've run gofmt on the file, because indentation looks
inconsistent in places.


https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms.go
File state/apiserver/charms.go (right):

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms.go#newcode125
state/apiserver/charms.go:125: for _, file := range reader.File {
gofmt again?

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms.go#newcode138
state/apiserver/charms.go:138: } else {
Instead of else, you could just return in the if block above.

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms.go#newcode511
state/apiserver/charms.go:511: // processGet handles a charm file
download GET request after authentication.
s/download//

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms.go#newcode546
state/apiserver/charms.go:546: // save the corresponding zip archive to
the given charmArchivePath.
s/save/saves/

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms.go#newcode580
state/apiserver/charms.go:580: if err =
os.Rename(tempCharmArchive.Name(), charmArchivePath); err != nil {
In this case I think you should defer os.Remove(tempCharmArchive.Name())
here.

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go
File state/apiserver/charms_test.go (right):

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode265
state/apiserver/charms_test.go:265: func (s *charmsSuite)
TestGetReturnsFileNotFound(c *gc.C) {
s/TestGetReturnsFileNotFound/TestGetReturnsNotFoundWhenMissing/ ?

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode271
state/apiserver/charms_test.go:271: // Ensure a 404 is returned fo files
not included in the charm.
s/fo/for/

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode271
state/apiserver/charms_test.go:271: // Ensure a 404 is returned fo files
not included in the charm.
Please, put a blank line before this one, for readability (I'll use "b"
in all similar cases below).

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode283
state/apiserver/charms_test.go:283: func (s *charmsSuite)
TestGetReturnsDirectoryForbidden(c *gc.C) {
Similarly,
s/TestGetReturnsDirectoryForbidden/TestGetReturnsForbiddenWithDirectory/
?

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode289
state/apiserver/charms_test.go:289: // Ensure a 403 is returned if the
requested file is a directory.
b

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode302
state/apiserver/charms_test.go:302: // Ensure the file contents are
properly returned.
b

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode335
state/apiserver/charms_test.go:335: // Ensure charm files are properly
listed.
b

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode353
state/apiserver/charms_test.go:353: // Create and save the zip archive.
b

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode367
state/apiserver/charms_test.go:367: // Ensure the cached contents are
properly retrieved.
b

https://codereview.appspot.com/67750045/diff/20001/state/apiserver/charms_test.go#newcode441
state/apiserver/charms_test.go:441: ctype :=
resp.Header.Get("content-type")
s/content-type/Content-Type/

https://codereview.appspot.com/67750045/