[V3] Update code standards (black code format pass) (#1650)

* ran black: code formatter against `redbot/` with `-l 99`

* badge

redbot/cogs/bank/errors.py

@@ -1,6 +1,7 @@
 class BankError(Exception):
     pass
 
+
 class BankNotGlobal(BankError):
     pass
 
@@ -34,4 +35,4 @@ class NegativeValue(BankError):
 
 
 class SameSenderAndReceiver(BankError):
-    pass
+    pass