Add `pragma: no cover` directive to b.e.server.addServer.
Add `pragma: no cover` directive to b.e.server.addServer.

We don't need to test for conditions which might raise a
``twisted.protocols.tcp.CannotListenError``, we just need to ensure that
we exit if we can't bind to the port for the email server.

pagea/bridgedb,pagea/bridgedb