Fix darker complaint, even though inconsistent

IPython/terminal/interactiveshell.py

@@ -248,7 +248,7 b' class TerminalInteractiveShell(InteractiveShell):'
             self.reformat_handler = lambda x:x
         elif formatter == 'black':
             self.reformat_handler = black_reformat_handler
-        elif formatter == 'yapf':
+        elif formatter == "yapf":
             self.reformat_handler = yapf_reformat_handler
         else:
             raise ValueError