Enhancement/url error

Fixes a misleading error when the host does not have an URL prefix, or is an invalid URL.

This is an issue because in requests, if the URL is invalid, we get an error before the pre_request hook runs. Which in this case, means that the on_pre_request method that fills request_meta does not run.

This creates a issue because then, we get a KeyError a couple of lines down the road, which does not indicate where the error is coming from (because start_time is not there).


This pull request re-raises the exceptions raised in the full_url method of request's Request object.