Use Python 3.8 on OSX for Foxy (ros2#663)

* Use Python 3.8 on OSX for Foxy

Replaces ros2#641

* Add Python 3.8 Install instructions to osx Dev setup page

Signed-off-by: Shane Loretz <[email protected]>

* Delete python3 from one line

Signed-off-by: Shane Loretz <[email protected]>

Author: sloretz

source/Installation/Foxy/macOS-Development-Setup.rst

@@ -55,7 +55,12 @@ You need the following things installed to build ROS 2:
 
    .. code-block:: bash
 
-       brew install cmake cppcheck eigen pcre poco python3 tinyxml wget bullet
+       brew install cmake cppcheck eigen pcre poco tinyxml wget bullet
+
+       brew install [email protected]
+       brew unlink python
+       # Make the python command be Python 3.8
+       brew link --force [email protected]
 
        # install dependencies for Fast-RTPS if you are using it
        brew install asio tinyxml2

source/Installation/Foxy/macOS-Install-Binary.rst

@@ -44,7 +44,11 @@ You need the following things installed before installing ROS 2.
 
   .. code-block:: bash
 
-       brew install python3
+       brew install [email protected]
+       # Unlink in case you have [email protected] installed already
+       brew unlink python
+       # Make the python command be Python 3.8
+       brew link --force [email protected]
 
        # install asio and tinyxml2 for Fast-RTPS
        brew install asio tinyxml2