Backport PR #1939: Add debug log for static file paths

Too often I'm trying to track down an errant extra static file path (like some javascript installed in some obscure place). This makes it easy to see exactly what is being served.

Signed-off-by: Min RK <benjaminrk@gmail.com>

Author: minrk

notebook/base/handlers.py

@@ -40,6 +40,12 @@
 
 sys_info = json.dumps(get_sys_info())
 
+def log():
+    if Application.initialized():
+        return Application.instance().log
+    else:
+        return app_log
+
 class AuthenticatedHandler(web.RequestHandler):
     """A RequestHandler with an authenticated user."""
 
@@ -152,10 +158,7 @@ def config(self):
     @property
     def log(self):
         """use the IPython log by default, falling back on tornado's logger"""
-        if Application.initialized():
-            return Application.instance().log
-        else:
-            return app_log
+        return log()
 
     @property
     def jinja_template_vars(self):
@@ -547,6 +550,9 @@ def get_absolute_path(cls, roots, path):
                 return ''
 
             cls._static_paths[path] = abspath
+            
+
+            log().debug("Path %s served from %s"%(path, abspath))
             return abspath
 
     def validate_absolute_path(self, root, absolute_path):