verify behavior if there is a poorly behaved plugin

src/allmydata/test/storage_plugin.py

@@ -42,6 +42,9 @@ class DummyStorage(object):
     name = attr.ib()
 
     def get_storage_server(self, configuration, get_anonymous_storage_server):
+        if u"invalid" in configuration:
+            raise Exception("The plugin is unhappy.")
+
         announcement = {u"value": configuration.get(u"some", u"default-value")}
         storage_server = DummyStorageServer(get_anonymous_storage_server)
         return succeed(

src/allmydata/test/test_client.py

@@ -27,9 +27,11 @@ from testtools.matchers import (
     MatchesListwise,
     MatchesDict,
     MatchesStructure,
+    Always,
 )
 from testtools.twistedsupport import (
     succeeded,
+    failed,
 )
 
 import allmydata
@@ -1320,3 +1322,30 @@ introducer.furl = pb://abcde@nowhere/fake
                 ]),
             )),
         )
+
+
+    def test_broken_storage_plugin(self):
+        """
+        A storage plugin that raises an exception from ``get_storage_server``
+        causes ``client.create_client_from_config`` to return ``Deferred``
+        that fails.
+        """
+        self.useFixture(UseTestPlugins())
+
+        config = client.config_from_string(
+            self.basedir,
+            u"tub.port",
+            self.get_config(
+                storage_enabled=True,
+                more_storage=b"plugins=tahoe-lafs-dummy-v1",
+                more_sections=(
+                    b"[storageserver.plugins.tahoe-lafs-dummy-v1]\n"
+                    # This will make it explode on instantiation.
+                    b"invalid = configuration\n"
+                )
+            ),
+        )
+        self.assertThat(
+            client.create_client_from_config(config, introducer_factory=MemoryIntroducerClient),
+            failed(Always()),
+        )