fix regression in KM. be sure to raise an exception when a kernel doesn't start properly

Author: Zsailer

jupyter_client/manager.py

@@ -76,6 +76,7 @@ async def wrapper(self, *args, **kwargs):
         except Exception as e:
             self._ready.set_exception(e)
             self.log.exception(self._ready.exception())
+            raise e
 
     return wrapper
 

jupyter_client/multikernelmanager.py

@@ -207,7 +207,6 @@ async def _async_start_kernel(self, kernel_name: t.Optional[str] = None, **kwarg
         starter = ensure_async(km.start_kernel(**kwargs))
         fut = asyncio.ensure_future(self._add_kernel_when_ready(kernel_id, km, starter))
         self._pending_kernels[kernel_id] = fut
-
         # Handling a Pending Kernel
         if self._using_pending_kernels():
             # If using pending kernels, do not block