Adding messages to HTTPError raising.

These messages are not returned to the browser, but are printed
to the server logs and will help the code readability.
I have also used a more specific code in some cases.

IPython/frontend/html/notebook/handlers.py

@@ -53,7 +53,7 b' class NamedNotebookHandler(web.RequestHandler):'
     def get(self, notebook_id):
         nbm = self.application.notebook_manager
         if not nbm.notebook_exists(notebook_id):
-            raise web.HTTPError(404)
+            raise web.HTTPError(404, u'Notebook does not exist: %s' % notebook_id)
         self.render('notebook.html', notebook_id=notebook_id)
 
 
@@ -311,7 +311,7 b' class RSTHandler(web.RequestHandler):'
 
     def post(self):
         if publish_string is None:
-            raise web.HTTPError(503)
+            raise web.HTTPError(503, u'docutils not available')
         body = self.request.body.strip()
         source = body
         # template_path=os.path.join(os.path.dirname(__file__), u'templates', u'rst_template.html')
@@ -326,7 +326,7 b' class RSTHandler(web.RequestHandler):'
                                   settings_overrides=defaults
             )
         except:
-            raise web.HTTPError(400)
+            raise web.HTTPError(400, u'Invalid RST')
         print html
         self.set_header('Content-Type', 'text/html')
         self.finish(html)

IPython/frontend/html/notebook/kernelmanager.py

@@ -278,24 +278,20 b' class MappingKernelManager(KernelManager):'
 
     def kill_kernel(self, kernel_id):
         """Kill a kernel and remove its notebook association."""
-        if kernel_id not in self:
-            raise web.HTTPError(404)
+        self._check_kernel_id(kernel_id)
         super(MappingKernelManager, self).kill_kernel(kernel_id)
         self.delete_mapping_for_kernel(kernel_id)
         self.log.info("Kernel killed: %s" % kernel_id)
 
     def interrupt_kernel(self, kernel_id):
         """Interrupt a kernel."""
-        if kernel_id not in self:
-            raise web.HTTPError(404)
+        self._check_kernel_id(kernel_id)
         super(MappingKernelManager, self).interrupt_kernel(kernel_id)
         self.log.info("Kernel interrupted: %s" % kernel_id)
 
     def restart_kernel(self, kernel_id):
         """Restart a kernel while keeping clients connected."""
-        if kernel_id not in self:
-            raise web.HTTPError(404)
-
+        self._check_kernel_id(kernel_id)
         # Get the notebook_id to preserve the kernel/notebook association.
         notebook_id = self.notebook_for_kernel(kernel_id)
         # Create the new kernel first so we can move the clients over.
@@ -309,17 +305,22 b' class MappingKernelManager(KernelManager):'
         return new_kernel_id
 
     def create_iopub_stream(self, kernel_id):
-        if kernel_id not in self:
-            raise web.HTTPError(404)
+        """Create a new iopub stream."""
+        self._check_kernel_id(kernel_id)
         return super(MappingKernelManager, self).create_iopub_stream(kernel_id)
 
     def create_shell_stream(self, kernel_id):
-        if kernel_id not in self:
-            raise web.HTTPError(404)
+        """Create a new shell stream."""
+        self._check_kernel_id(kernel_id)
         return super(MappingKernelManager, self).create_shell_stream(kernel_id)
 
     def create_hb_stream(self, kernel_id):
-        if kernel_id not in self:
-            raise web.HTTPError(404)
+        """Create a new hb stream."""
+        self._check_kernel_id(kernel_id)
         return super(MappingKernelManager, self).create_hb_stream(kernel_id)
 
+    def _check_kernel_id(self, kernel_id):
+        """Check a that a kernel_id exists and raise 404 if not."""
+        if kernel_id not in self:
+            raise web.HTTPError(404, u'Kernel does not exist: %s' % kernel_id)
+

IPython/frontend/html/notebook/notebookmanager.py

@@ -93,7 +93,7 b' class NotebookManager(LoggingConfigurable):'
         try:
             name = self.mapping[notebook_id]
         except KeyError:
-            raise web.HTTPError(404)
+            raise web.HTTPError(404, u'Notebook does not exist: %s' % notebook_id)
         return self.get_path_by_name(name)
 
     def get_path_by_name(self, name):
@@ -106,7 +106,7 b' class NotebookManager(LoggingConfigurable):'
         """Get the representation of a notebook in format by notebook_id."""
         format = unicode(format)
         if format not in self.allowed_formats:
-            raise web.HTTPError(415)
+            raise web.HTTPError(415, u'Invalid notebook format: %s' % format)
         last_modified, nb = self.get_notebook_object(notebook_id)
         data = current.writes(nb, format)
         name = nb.get('name','notebook')
@@ -116,7 +116,7 b' class NotebookManager(LoggingConfigurable):'
         """Get the NotebookNode representation of a notebook by notebook_id."""
         path = self.find_path(notebook_id)
         if not os.path.isfile(path):
-            raise web.HTTPError(404)
+            raise web.HTTPError(404, u'Notebook does not exist: %s' % notebook_id)
         info = os.stat(path)
         last_modified = datetime.datetime.utcfromtimestamp(info.st_mtime)
         with open(path,'r') as f:
@@ -125,7 +125,7 b' class NotebookManager(LoggingConfigurable):'
                 # v1 and v2 and json in the .ipynb files.
                 nb = current.reads(s, u'json')
             except:
-                raise web.HTTPError(404)
+                raise web.HTTPError(500, u'Unreadable JSON notebook.')
         if 'name' not in nb:
             nb.name = os.path.split(path)[-1].split(u'.')[0]
         return last_modified, nb
@@ -137,18 +137,18 b' class NotebookManager(LoggingConfigurable):'
         and the value in the data is updated to use that value.
         """
         if format not in self.allowed_formats:
-            raise web.HTTPError(415)
+            raise web.HTTPError(415, u'Invalid notebook format: %s' % format)
 
         try:
             nb = current.reads(data, format)
         except:
-            raise web.HTTPError(400)
+            raise web.HTTPError(400, u'Invalid JSON data')
 
         if name is None:
             try:
                 name = nb.metadata.name
             except AttributeError:
-                raise web.HTTPError(400)
+                raise web.HTTPError(400, u'Missing notebook name')
         nb.metadata.name = name
 
         notebook_id = self.new_notebook_id(name)
@@ -158,12 +158,12 b' class NotebookManager(LoggingConfigurable):'
     def save_notebook(self, notebook_id, data, name=None, format=u'json'):
         """Save an existing notebook by notebook_id."""
         if format not in self.allowed_formats:
-            raise web.HTTPError(415)
+            raise web.HTTPError(415, u'Invalid notebook format: %s' % format)
 
         try:
             nb = current.reads(data, format)
         except:
-            raise web.HTTPError(400)
+            raise web.HTTPError(400, u'Invalid JSON data')
 
         if name is not None:
             nb.metadata.name = name
@@ -172,18 +172,18 b' class NotebookManager(LoggingConfigurable):'
     def save_notebook_object(self, notebook_id, nb):
         """Save an existing notebook object by notebook_id."""
         if notebook_id not in self.mapping:
-            raise web.HTTPError(404)
+            raise web.HTTPError(404, u'Notebook does not exist: %s' % notebook_id)
         old_name = self.mapping[notebook_id]
         try:
             new_name = nb.metadata.name
         except AttributeError:
-            raise web.HTTPError(400)
+            raise web.HTTPError(400, u'Missing notebook name')
         path = self.get_path_by_name(new_name)
         try:
             with open(path,'w') as f:
                 current.write(nb, f, u'json')
         except:
-            raise web.HTTPError(400)
+            raise web.HTTPError(400, u'Unexpected error while saving notebook')
         if old_name != new_name:
             old_path = self.get_path_by_name(old_name)
             if os.path.isfile(old_path):
@@ -195,7 +195,7 b' class NotebookManager(LoggingConfigurable):'
         """Delete notebook by notebook_id."""
         path = self.find_path(notebook_id)
         if not os.path.isfile(path):
-            raise web.HTTPError(404)
+            raise web.HTTPError(404, u'Notebook does not exist: %s' % notebook_id)
         os.unlink(path)
         self.delete_notebook_id(notebook_id)