Fix exception causes in 5 modules

Author: cool-RR

jupyter_server/base/handlers.py

@@ -470,10 +470,10 @@ def get_json_body(self):
         body = self.request.body.strip().decode(u'utf-8')
         try:
             model = json.loads(body)
-        except Exception:
+        except Exception as e:
             self.log.debug("Bad JSON: %r", body)
             self.log.error("Couldn't parse JSON", exc_info=True)
-            raise web.HTTPError(400, u'Invalid JSON in body of request')
+            raise web.HTTPError(400, u'Invalid JSON in body of request') from e
         return model
 
     def write_error(self, status_code, **kwargs):

jupyter_server/extension/handler.py

@@ -75,7 +75,7 @@ def static_url(self, path, include_host=None, **kwargs):
                 raise Exception(
                     "This extension doesn't have any static paths listed. Check that the "
                     "extension's `static_paths` trait is set."
-                )
+                ) from e
             else:
                 raise e
 

jupyter_server/extension/serverextension.py

@@ -149,8 +149,10 @@ def _get_load_jupyter_server_extension(obj):
         func = getattr(obj, '_load_jupyter_server_extension')
     except AttributeError:
         func = getattr(obj, 'load_jupyter_server_extension')
-    except:
-        raise ExtensionLoadingError("_load_jupyter_server_extension function was not found.")
+    except BaseException:
+        raise ExtensionLoadingError(
+            "_load_jupyter_server_extension function was not found."
+        ) from e
     return func
 
 
@@ -178,8 +180,8 @@ def validate_server_extension(name):
     try:
         mod, metadata = _get_server_extension_metadata(name)
         version = getattr(mod, '__version__', '')
-    except ImportError:
-        raise ExtensionValidationError('{} is not importable.'.format(name))
+    except ImportError as e:
+        raise ExtensionValidationError('{} is not importable.'.format(name)) from e
 
     try:
         for item in metadata:
@@ -193,8 +195,10 @@ def validate_server_extension(name):
             else:
                 raise AttributeError
     # If the extension does not have a `load_jupyter_server_extension` function, raise exception.
-    except AttributeError:
-        raise ExtensionValidationError('Found "{}" module but cannot load it.'.format(name))
+    except AttributeError as e:
+        raise ExtensionValidationError(
+            'Found "{}" module but cannot load it.'.format(name)
+        ) from e
     return version
 
 

jupyter_server/gateway/managers.py

@@ -279,18 +279,18 @@ async def gateway_request(endpoint, **kwargs):
     # or the server is not running.
     # NOTE: We do this here since this handler is called during the Notebook's startup and subsequent refreshes
     # of the tree view.
-    except ConnectionRefusedError:
+    except ConnectionRefusedError as e:
         raise web.HTTPError(503, "Connection refused from Gateway server url '{}'.  "
-              "Check to be sure the Gateway instance is running.".format(GatewayClient.instance().url))
+              "Check to be sure the Gateway instance is running.".format(GatewayClient.instance().url)) from e
     except HTTPError as e:
         # This can occur if the host is valid (e.g., foo.com) but there's nothing there.
         raise web.HTTPError(e.code, "Error attempting to connect to Gateway server url '{}'.  "
                        "Ensure gateway url is valid and the Gateway instance is running.".
-                            format(GatewayClient.instance().url))
-    except gaierror:
+                            format(GatewayClient.instance().url)) from e
+    except gaierror as e:
         raise web.HTTPError(404, "The Gateway server specified in the gateway_url '{}' doesn't appear to be valid.  "
                        "Ensure gateway url is valid and the Gateway instance is running.".
-                            format(GatewayClient.instance().url))
+                            format(GatewayClient.instance().url)) from e
 
     return response
 
@@ -552,8 +552,10 @@ async def get_kernel_spec(self, kernel_name, **kwargs):
             if error.status_code == 404:
                 # Convert not found to KeyError since that's what the Notebook handler expects
                 # message is not used, but might as well make it useful for troubleshooting
-                raise KeyError('kernelspec {kernel_name} not found on Gateway server at: {gateway_url}'.
-                               format(kernel_name=kernel_name, gateway_url=GatewayClient.instance().url))
+                raise KeyError(
+                    'kernelspec {kernel_name} not found on Gateway server at: {gateway_url}'.
+                    format(kernel_name=kernel_name, gateway_url=GatewayClient.instance().url)
+                ) from error
             else:
                 raise
         else:

jupyter_server/serverapp.py

@@ -44,12 +44,12 @@
 # check for tornado 3.1.0
 try:
     import tornado
-except ImportError:
-    raise ImportError(_("The Jupyter Server requires tornado >= 4.0"))
+except ImportError as e:
+    raise ImportError(_("The Jupyter Server requires tornado >= 4.0")) from e
 try:
     version_info = tornado.version_info
-except AttributeError:
-    raise ImportError(_("The Jupyter Server requires tornado >= 4.0, but you have < 1.1.0"))
+except AttributeError as e:
+    raise ImportError(_("The Jupyter Server requires tornado >= 4.0, but you have < 1.1.0")) from e
 if version_info < (4,0):
     raise ImportError(_("The Jupyter Server requires tornado >= 4.0, but you have %s") % tornado.version)
 
@@ -1681,12 +1681,12 @@ def http_server(self):
         """An instance of Tornado's HTTPServer class for the Server Web Application."""
         try:
             return self._http_server
-        except AttributeError:
+        except AttributeError as e:
             raise AttributeError(
                 'An HTTPServer instance has not been created for the '
                 'Server Web Application. To create an HTTPServer for this '
                 'application, call `.init_httpserver()`.'
-                )
+                ) from e
 
     def init_httpserver(self):
         """Creates an instance of a Tornado HTTPServer for the Server Web Application