[ScmRepoLink] Cannot link an app to a repo link

[johnsudaar]

When checking if the app is already linked, we use the following condition:

if scerr, ok := errors.ErrgoRoot(err).(*http.RequestFailedError); ok || (ok && scerr.Code != 404) {
	return errgo.Notef(err, "fail to get the integration link for this app")
}

Howerver if there is a 404 error (which is likely since the app should not be linked), err will be something like:

&http.RequestFailedError{
  Code: 404
}

So ok will be true.

Since the condition for failure is:

ok || (ok && scerr.Code != 404)

This will be true || false => true and we will fail.

[johnsudaar]

This bug was introduced here: https://github.com/Scalingo/cli/pull/515/files