Change instructions to use bash-completion2 on OS X per xonsh#2111

docs/osx.rst

@@ -47,11 +47,11 @@ On Mac OSX, it is *strongly* recommended to install the ``gnureadline`` library
 
     $ pip3 install gnureadline
 
-Xonsh has support for using bash completion files on the shell, to use it you need to install the bash-completion package
+Xonsh has support for using bash completion files on the shell, to use it you need to install the bash-completion package. The regular bash-completion package uses v1 which mostly works, but `occasionally has rough edges <https://github.com/xonsh/xonsh/issues/2111>`_ so we recommend using bash-completion v2 which is installed using the bash-completion2 package.
 
 .. code-block:: console
 
-    $ brew install bash-completion
+    $ brew install bash-completion2
 
 .. include:: dependencies.rst