fix a typo, add a comment. about @require and heterogenous clients.

docs/source/parallel/parallel_multiengine.txt

@@ -677,7 +677,10 b' You can also specify imports via the ``@require`` decorator. This is a decorato'
 designed for use in Dependencies, but can be used to handle remote imports as well.
 Modules or module names passed to ``@require`` will be imported before the decorated
 function is called.  If they cannot be imported, the decorated function will never
-execution, and will fail with an UnmetDependencyError.
+execute and will fail with an UnmetDependencyError.
+
+..
+    what about single engines failing to import? will none of them execute the function?
 
 .. sourcecode:: ipython