Get the path manipulation into _Config too

src/allmydata/client.py

@@ -465,17 +465,16 @@ def create_introducer_clients(config, main_tub, _introducer_factory=None):
 
     introducers = config.get_introducer_configuration()
 
-    for petname, introducer_furl in introducers.items():
-        introducer_cache_filepath = FilePath(config.get_private_path("introducer_{}_cache.yaml".format(petname)))
+    for petname, (furl, cache_path) in introducers.items():
         ic = _introducer_factory(
             main_tub,
-            introducer_furl.encode("ascii"),
+            furl.encode("ascii"),
             config.nickname,
             str(allmydata.__full_version__),
             str(_Client.OLDEST_SUPPORTED_VERSION),
             list(node.get_app_versions()),
             partial(_sequencer, config),
-            introducer_cache_filepath,
+            cache_path,
         )
         introducer_clients.append(ic)
     return introducer_clients

src/allmydata/node.py

@@ -438,12 +438,17 @@ class _Config(object):
         """
         Get configuration for introducers.
 
-        :return {unicode: unicode}: A mapping from introducer petname to the
-            introducer's fURL.
+        :return {unicode: (unicode, FilePath)}: A mapping from introducer
+            petname to a tuple of the introducer's fURL and local cache path.
         """
         introducers_yaml_filename = self.get_private_path("introducers.yaml")
         introducers_filepath = FilePath(introducers_yaml_filename)
 
+        def get_cache_filepath(petname):
+            return FilePath(
+                self.get_private_path("introducer_{}_cache.yaml".format(petname)),
+            )
+
         try:
             with introducers_filepath.open() as f:
                 introducers_yaml = safe_load(f)
@@ -491,7 +496,11 @@ class _Config(object):
             )
             introducers['default'] = tahoe_cfg_introducer_furl
 
-        return introducers
+        return {
+            petname: (furl, get_cache_filepath(petname))
+            for (petname, furl)
+            in introducers.items()
+        }
 
 
 def create_tub_options(config):