Copied environment variables test and comment over
Addressed review comment: Added separate test for environment variable usage in isolation, without moving.
Addressed review comment: Moved `addCleanup`s
Addressed review comment: Hardcoded SQL queries
Added PyMySQL to setup.py
Skip relevant tests if PyMySQL is not installed
Merge forward.
Don't include errno in pymysql error string.

The errno varies between osx and linux.
Add some comments.
Make sure to close connection to node 1.
Don't test autoincrement behavior.
Merge pull request #998 from ClusterHQ/mysql-test-FLOC-1044

[FLOC-1044] MySQL Acceptance test

Author: @adamtheturtle
Reviewers: @itamarst, @tomprince