DEV: Add re-raise toggle for server extensions.

Also renames toggles to "reraise_*_extension_failures".

IPython/core/shellapp.py

@@ -143,7 +143,7 b' class InteractiveShellApp(Configurable):'
     reraise_ipython_extension_failures = Bool(
         False,
         config=True,
-        help="If True, exit on failure to load any extensions.",
+        help="Reraise exceptions encountered loading IPython extensions?",
     )
 
     # Extensions that are always loaded (not configurable)
@@ -265,7 +265,7 b' class InteractiveShellApp(Configurable):'
                     self.log.info("Loading IPython extension: %s" % ext)
                     self.shell.extension_manager.load_extension(ext)
                 except:
-                    if self.exit_on_extension_load_failure:
+                    if self.reraise_ipython_extension_failures:
                         raise
                     msg = ("Error in loading extension: {ext}\n"
                            "Check your config files in {location}".format(
@@ -274,7 +274,7 b' class InteractiveShellApp(Configurable):'
                            ))
                     self.log.warn(msg, exc_info=True)
         except:
-            if self.exit_on_extension_load_failure:
+            if self.reraise_ipython_extension_failures:
                 raise
             self.log.warn("Unknown error in loading extensions:", exc_info=True)
 

IPython/html/notebookapp.py

@@ -751,6 +751,12 b' class NotebookApp(BaseIPythonApplication):'
               "This is an experimental API, and may change in future releases.")
     )
 
+    reraise_server_extension_failures = Bool(
+        False,
+        config=True,
+        help="Reraise exceptions encountered loading server extensions?",
+    )
+
     def parse_command_line(self, argv=None):
         super(NotebookApp, self).parse_command_line(argv)
         
@@ -984,6 +990,8 b' class NotebookApp(BaseIPythonApplication):'
                 if func is not None:
                     func(self)
             except Exception:
+                if self.reraise_server_extension_failures:
+                    raise
                 self.log.warn("Error loading server extension %s", modulename,
                               exc_info=True)