Save the whole environment in setup and restore it in teardown, so all the other tests messing with the environment variables also benefit from this.
Save the whole environment in setup and restore it in teardown, so all
the other tests messing with the environment variables also benefit from
this.

oubiwann/txaws,twisted/txaws,twisted/txaws,mithrandi/txaws,mithrandi/txaws,oubiwann/txaws