* If there's no python or there's only python2.6 on red hat systems, install python3
* Always check for python2.6
* address style, documentation, nits
* factor out all initialization code
* fix up python version return value when no python installed
* add no python error and exit
* document DeterminePythonVersion parameters
* build letsencrypt-auto
* close brace
* build leauto
* fix syntax errors
* set USE_PYTHON_3 for all cases
* rip out NOCRASH
* replace NOCRASH, update LE_PYTHON set logic
* use built-in venv for py3
* switch to LE_PYTHON not affecting bootstrap selection and not overwriting LE_PYTHON
* python3ify fetch.py
* get fetch.py working with python2 and 3
* don't verify server certificates in fetch.py HttpsGetter
* Use SSLContext and an environment variable so that our tests continue to never verify server certificates.
* typo
* build
* remove commented out code
* address review comments
* add documentation for YES_FLAG and QUIET_FLAG
* Add tests to centos6 Dockerfile to make sure we install python3 if and only if appropriate to do so.
* Use pipstrap to install a good version of pip
* Use pytest in cb-auto tests
* Remove nose usage in auto_test.py
* remove nose dev dep
* use pytest in test_tests
* Use pytest in tox
* Update dev dependency pinnings
* remove nose multiprocess lines
* Use pytest for coverage
* Use older py and pytest for old python versions
* Add test for Error.__str__
* pin pytest in oldest test
* Fix tests for DNS-DO plugin on py26
* Work around bug for Python 3.3
* Clarify dockerfile comments
