Create loop in get_event_loop if needed

This fixes issue #702.

Author: zvyn

uvloop/__init__.py

@@ -203,10 +203,7 @@ def get_event_loop(self) -> _AbstractEventLoop:
             Returns an instance of EventLoop or raises an exception.
             """
             if self._local._loop is None:
-                raise RuntimeError(
-                    'There is no current event loop in thread %r.'
-                    % threading.current_thread().name
-                )
+                self._local._loop = self._loop_factory()
 
             return self._local._loop