Run pylint in Python 3

Currently run_pylint.sh only runs in tox environment py27-lint.
py35-lint uses another script named run_mini_py3lint.sh.

1. Make run_pylint.sh run and pass for py35-lint. Might have to add some ignores to .pylintrc (such as useless-object-inheritance), and might have to rename some deprecated functions (such as s/assertRaisesRegexp/assertRaisesRegex/).
2. Make sure all tests in run_mini_py3lint.sh are in run_pylint.sh and remove run_mini_py3lint.sh.
3. (optional) Remove py27-lint?