make generated config files more lintable

c, load_config are injected into the file namespace,
but linters don't know that

avoids `c is undefined` errors on every config line

uses `# noqa` to avoid lint on the `c = load_config()`  line itself

traitlets/config/application.py

@@ -941,6 +941,8 @@ def generate_config_file(self, classes=None):
         """generate default config file from Configurables"""
         lines = ["# Configuration file for %s." % self.name]
         lines.append("")
+        lines.append("c = get_config()  # noqa")
+        lines.append("")
         classes = self.classes if classes is None else classes
         config_classes = list(self._classes_with_config_traits(classes))
         for cls in config_classes: