U file attribute was deprecated around 3.3
diff --git a/sopel/plugins/handlers.py b/sopel/plugins/handlers.py
index 76902aa..944f6c3 100644
--- a/sopel/plugins/handlers.py
+++ b/sopel/plugins/handlers.py
@@ -432,7 +432,7 @@ class PyFilePlugin(PyModulePlugin):
         # TODO: switch to ``importlib`` when Python2 support is dropped.
         if self.module_type == imp.PY_SOURCE:
             with open(self.path) as mod:
-                description = ('.py', 'U', self.module_type)
+                description = ('.py', 'r', self.module_type)
                 mod = imp.load_module(self.name, mod, self.path, description)
         elif self.module_type == imp.PKG_DIRECTORY:
             description = ('', '', self.module_type)