Beef up mentions of the need for Invoke, when using Match exec, in th…

…e docs

sites/docs/api/config.rst

@@ -61,11 +61,15 @@ Paramiko releases) are included. A keyword by itself means no known departures.
 
 - ``Host``
 - ``HostName``: used in ``%h`` :ref:`token expansion <TOKENS>`
-- ``Match``: fully supported, with the usual caveat that connection-time
-  information is not present during config lookup, and thus cannot be used to
-  determine matching. This primarily impacts ``Match user``, which can match
-  against loaded ``User`` values but has no knowledge about connection-time
-  usernames.
+- ``Match``: fully supported, with the following caveats:
+
+    - You must have the optional dependency Invoke installed; see :ref:`the
+      installation docs <paramiko-itself>` (in brief: install
+      ``paramiko[invoke]`` or ``paramiko[everything]``).
+    - As usual, connection-time information is not present during config
+      lookup, and thus cannot be used to determine matching. This primarily
+      impacts ``Match user``, which can match against loaded ``User`` values
+      but has no knowledge about connection-time usernames.
 
     .. versionadded:: 2.7
 

sites/www/installing.rst

@@ -37,7 +37,8 @@ There are also a number of **optional dependencies** you may install using
 .. TODO 3.0: tweak the ed25519 line to remove the caveat
 
 - If you want all optional dependencies at once, use ``paramiko[everything]``.
-- For ``Match exec`` config support, use ``paramiko[invoke]``.
+- For ``Match exec`` config support, use ``paramiko[invoke]`` (which installs
+  `Invoke <https://www.pyinvoke.org>`_).
 - For GSS-API / SSPI support, use ``paramiko[gssapi]``, though also see
   :ref:`the below subsection on it <gssapi>` for details.
 - ``paramiko[ed25519]`` references the dependencies for Ed25519 key support.