Update docs

Author: mlech-reef

.gitignore

@@ -4,6 +4,7 @@
 .eggs/
 .idea
 .nox/
+.python-version
 b2.egg-info
 build
 coverage.xml

README.md

@@ -256,35 +256,70 @@ We encourage outside contributors to perform changes on our codebase. Many such
 
 * provide guidance (through the issue reporting system)
 * provide tool assisted code review (through the Pull Request system)
+* maintain a set of unit tests
 * maintain a set of integration tests (run with a production cloud)
-* maintain a set of (well over a hundred) unit tests
-* automatically run unit tests on 14 versions of python (including osx, Jython and pypy)
-* format the code automatically using [yapf](https://github.com/google/yapf)
-* use static code analysis to find subtle/potential issues with maintainability
-* maintain other Continous Integration tools (coverage tracker)
-
-You'll need to some Python packages installed.  To get all the latest things:
-
-* `pip install --upgrade --upgrade-strategy eager -r requirements.txt -r requirements-test.txt -r requirements-setup.txt`
-
-There is a `Makefile` with a rule to run the unit tests using the currently active Python:
-
-    make setup
-    make test
-
-will install the required packages, then run the unit tests.
-
-To test in multiple python virtual environments, set the enviroment variable `PYTHON_VIRTUAL_ENVS`
-to be a space-separated list of their root directories.  When set, the makefile will run the
-unit tests in each of the environments.
-
-Before checking in, use the `pre-commit.sh` script to check code formatting, run
-unit tests, run integration tests etc.
-
-The integration tests need a file in your home directory called `.b2_auth`
-that contains two lines with nothing on them but your application key ID and application key:
-
-     applicationKeyId
-     applicationKey
+* maintain development automation tools using [nox](https://github.com/theacodes/nox) that can easily:
+   * format the code using [yapf](https://github.com/google/yapf)
+   * runs linters to find subtle/potential issues with maintainability
+   * run the test suite on multiple Python versions using [pytest](https://github.com/pytest-dev/pytest)
+* maintain Continuous Integration (by using GitHub Actions) that:
+   * runs all sorts of linters
+   * checks if the Python distribution can be built
+   * runs all tests on a matrix of 6 versions of Python (including pypy) and 3 operating systems (Linux, Mac OS X and Windows)
+   * checks if the documentation can be built properly
+* maintain other Continuous Integration tools (coverage tracker)
+
+You'll need to have [nox](https://github.com/theacodes/nox) installed:
+
+* `pip install nox`
+
+With `nox`, you can run different sessions (default are `lint` and `test`):
+
+* `format` -> Format the code.
+* `lint` -> Run linters.
+* `test` (`test-3.5`, `test-3.6`, `test-3.7`, `test-3.8`) -> Run test suite.
+* `cover` -> Perform coverage analysis.
+* `build` -> Build the distribution.
+* `deploy` -> Deploy the distribution to the PyPi.
+* `doc` -> Build the documentation.
+* `doc_cover` -> Perform coverage analysis for the documentation.
+
+For example:
+
+    $ nox -s format
+    nox > Running session format
+    nox > Creating virtual environment (virtualenv) using python3.8 in .nox/format
+    ...
+
+    $ nox --no-venv -s format
+    nox > Running session format
+    ...
+
+    $ nox -s test
+    nox > Running session test-3.5
+    ...
+    nox > Running session test-3.6
+    ...
+    nox > Running session test-3.7
+    ...
+    nox > Running session test-3.8
+    ...
+
+    $ nox -s test-3.8
+    nox > Running session test-3.8
+    nox > Re-using existing virtual environment at .nox/test-3-8.
+    ...
+
+Session `test` can run on many python versions.
+In order to do it, given Python interpreter must be installed in the operating system or via [pyenv](https://github.com/pyenv/pyenv).
+
+Sessions other than `test` use the latest stable Python. You can change it:
+
+    export PYTHON_DEFAULT_VERSION=3.7
+
+The integration tests need two environment variables:
+
+    export TEST_APPLICATION_KEY=your_app_key
+    export TEST_APPLICATION_KEY_ID=your_app_key_id
 
 We marked the places in the code which are significantly less intuitive than others in a special way. To find them occurrences, use `git grep '*magic*'`.