Updated log info for local content provider

Author: GladysNalvarte

repo2docker/contentproviders/base.py

@@ -70,4 +70,4 @@ def fetch(self, spec, output_dir, yield_output=False):
         msg = "Local content provider assumes {} == {}".format(spec['path'],
                                                                output_dir)
         assert output_dir == spec['path'], msg
-        yield
+        yield "Using local repo {}.\n".format(spec['path'])