Updated py-foolscap to 0.12.5.

* Release 0.12.5 (07-Dec-2016)

** Connection Status Reporting

This release adds an object named `ConnectionInfo`, which encapsulates
information about a connection (both progress while being established, and
the outcome once connected). This includes which connection hint was
successful, what happened with the other hints, which handlers were used for
each, and when the connection was made or lost. To get one of these, use
`tub.getConnectionInfoForFURL(furl)` any time after `getReference()` is
called, or `rref.getConnectionInfo()` after it resolves.  #267

It also adds `ReconnectionInfo`, a similar object for Reconnectors. These
capture the state of reconnection process (trying, established, waiting), and
will provide a `ConnectionInfo` for the most recent (possibly successful)
connection attempt. The API is `reconnector.getReconnectionInfo()`.  #268

For details, see "Connection Progress/Status" and "Reconnector Status" in
`doc/using-foolscap.rst`.

** Connection Handler API Changes

To support `ConnectionInfo`, the Connection Handler API was changed.

The one backwards-incompatible change was that the `hint_to_endpoint()`
method now takes a third argument, to update the status as the handler makes
progress. External handler functions will need to be modified to accept this
new argument, and applications which use them should declare a dependency
upon the latest Foolscap version, to avoid runtime breakage.

Several backwards-compatible changes were made too: handlers can provide a
`describe()` method (which feeds `ConnectionInfo.connectionHandlers`), and
they can now set a special attribute on any exception they raise, to further
influence the status string.

In addition, the `tor.control_endpoint_maker()` handler now accepts an
optional second argument, which causes the maker function to be called with a
additional `update_status` argument. This backwards-compatible change allows
the maker function to influence the `ConnectionInfo` status too.

The Tor connection handler was enhanced to report distinct statuses for the
different phases of connection: launching a new copy of Tor, connecting to an
existing Tor daemon, etc.

** Minor Fixes

Foolscap-0.12.0 broke `flappserver create`, causing the command to hang
rather than exiting cleanly (although the flappserver directory itself was
probably created properly). This release finally fixes it.  #271


(wiz)