message: docs: update setup instructions
diff: @@ -50,21 +50,30 @@ We don't recommend using the system installed Python. Instead, first install the
  [homebrew](https://brew.sh/) manager and then run the following commands:
  ```
  -brew install pkg-config libffi openssl python
  -
  -env LDFLAGS="-L$(brew --prefix openssl)/lib" CFLAGS="-I$(brew --prefix openssl)/include" pip install cryptography==2.4.2
  +brew install readline pkg-config libffi openssl mysql postgres
  ```
  +You should install a recent version of Python (Superset uses 3.7.9). We'd recommend using a Python version manager like [pyenv](https://github.com/pyenv/pyenv) (and also [pyenv-virtualenv](https://github.com/pyenv/pyenv-virtualenv)).
  +
  Let's also make sure we have the latest version of `pip` and `setuptools`:
  ```
  pip install --upgrade setuptools pip
  ```
  +Lastly, you may need to set LDFLAGS and CFLAGS for certain Python packages to properly build. You can export these variables with:
  +
  +```
  +export LDFLAGS="-L$(brew --prefix openssl)/lib"
  +export CFLAGS="-I$(brew --prefix openssl)/include"
  +```
  +
  +These will now be available when pip installing requirements.
  +
  ### Python Virtual Environment
  We highly recommend installing Superset inside of a virtual environment. Python ships with
  -`virtualenv` out of the box but you can install it using:
  +`virtualenv` out of the box. If you're using [pyenv](https://github.com/pyenv/pyenv), you can install [pyenv-virtualenv](https://github.com/pyenv/pyenv-virtualenv). Or you can install it with `pip`:
  ```
  pip install virtualenv
  @@ -79,6 +88,14 @@ python3 -m venv venv
  . venv/bin/activate
  ```
  +Or with pyenv-virtualenv:
  +
  +```
  +# Here we name the virtual env 'superset'
  +pyenv virtualenv superset
  +pyenv activate superset
  +```
  +
  Once you activated your virtual environment, all of the Python packages you install or uninstall
  will be confined to this environment. You can exit the environment by running `deactivate` on the
  command line.
  