The error message from `python3 -m venv` when you don't have `python3-venv` installed is pretty good, but lets skip the failure and make sure it is installed the first time.
Fixes#7857.
* stop using urllib2 in test farm tests
* use six for urllib instead
* remove fabric lcd usage
* correct lcd removal
* remove fabric cd
* convert some remote calls to v2
* move more cxns to v2
* get run working with prefix
* get sudo commands working
* remove final fabric v1 references including local
* update requirements and README
* add new venv to gitignore
* update version used in travis
* remove deploy_script unused kwargs
* fix killboulder implementation so I can test creating a new boulder server
* hardcode the gopath due to broken env manamagement in fabric2
* Update letstest readme
* move the comment about hardcoding the ggopath
* catch BaseException instead of Exception
* work around fabric #2007
* use connections as context managers to ensure they're closed
* remove reference to virtualenv
