Update cheatsheets

tox

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# tox
+
+> Automate Python testing across multiple Python versions.
+> Use tox.ini to configure environments and test command.
+> More information: <https://github.com/tox-dev/tox>.
+
+- Run tests on all test environments:
+
+`tox`
+
+- Create a `tox.ini` configuration:
+
+`tox-quickstart`
+
+- List the available environments:
+
+`tox --listenvs-all`
+
+- Run tests on a specific environment (e.g. Python 3.6):
+
+`tox -e {{py36}}`
+
+- Force the virtual environment to be recreated:
+
+`tox --recreate -e {{py27}}`