fixup! Improve internal documentation (#6691)

test/integration_test.py

@@ -297,10 +297,11 @@ def _select_source(self,
         :param catalog: The name of the catalog to select a source from.
 
         :param public: If none (as by default), allow the source to be either
-        public or non-public. If true, choose a public source, or raise an
-        assertion if the catalog contains no public sources. If false, choose
-        a non-public source, or return `None` if the catalog contains no non-
-        public sources.
+                       public or non-public. If true, choose a public source, or
+                       raise an `AssertionError` if the catalog contains no
+                       public sources. If false, choose a non-public source, or
+                       return `None` if the catalog contains no non-public
+                       sources.
         """
         plugin = self.repository_plugin(catalog)
         sources = set(config.sources(catalog))