doc: use modern import style in runrst

hgweb: do not audit URL path as working-directory path Since hgweb is an interface to repository data, we don't need to prohibit any paths conflicting within the filesystem. Still an access to working files is audited by filectx.

hgweb: map Abort to 403 error to report inaccessible path for example Abort is so common in our codebase. We could instead introduce a dedicated type for path auditing errors, but we'll probably have to catch error.Abort anyway. As you can see, an abort message may include a full path to the repository, which might be considered information leak. If that matters, we should hide the message and send it to the server log instead.

hgweb: add error template to json so it won't crash