Changed the error message

Author: Chsudeepta

src/genie_python/genie_waitfor.py

@@ -357,7 +357,8 @@ def start_waiting(
 
         if block is not None:
             if not isinstance(block, str):
-                raise TypeError("First argument must be a valid block name or None, not {}".format(block))
+                raise TypeError("First argument must be a valid block name or None, not {}"
+                .format(block))
 
             if not self.api.block_exists(block):
                 raise NameError('No block with the name "{}" exists'.format(block))