bad error messages with bundle

[Matthieu Moy]

In addition to bug 58840, there are several unfriendly messages with the bundle stuff:

$ bzr pull /some/file

Complains about /some/file/ not being a branch. It should test whether the URL is a file, and give appropriate error message. Additionally, it could check the first line and point to "patch" in case the file seems to be a patch (i.e. something produced by "bzr diff" or "diff").

$ bzr pull /some/correct/bundle

Complains about branches having diverged when the bundle can't be pulled. This is not strictly incorrect, but the user will also be surprised to see the message talking about branch while he's applying a bundle. Probably "The bundle can not be applied because the branches have diverged" would be an improvement.