[Bank] Raise TypeError when passing a non-int transaction amount (#1976)

* Raise TypeError when passing a non-int bank amount

* Add a test

* Add some full stops

redbot/core/bank.py

@@ -214,8 +214,12 @@ async def withdraw_credits(member: discord.Member, amount: int) -> int:
     ValueError
         If the withdrawal amount is invalid or if the account has insufficient
         funds.
+    TypeError
+        If the withdrawal amount is not an `int`.
 
     """
+    if not isinstance(amount, int):
+        raise TypeError("Withdrawal amount must be of type int, not {}.".format(type(amount)))
     if _invalid_amount(amount):
         raise ValueError("Invalid withdrawal amount {} < 0".format(amount))
 
@@ -245,8 +249,12 @@ async def deposit_credits(member: discord.Member, amount: int) -> int:
     ------
     ValueError
         If the deposit amount is invalid.
+    TypeError
+        If the deposit amount is not an `int`.
 
     """
+    if not isinstance(amount, int):
+        raise TypeError("Deposit amount must be of type int, not {}.".format(type(amount)))
     if _invalid_amount(amount):
         raise ValueError("Invalid deposit amount {} <= 0".format(amount))
 
@@ -269,14 +277,18 @@ async def transfer_credits(from_: discord.Member, to: discord.Member, amount: in
     Returns
     -------
     int
-        The new balance.
+        The new balance of the member gaining credits.
 
     Raises
     ------
     ValueError
         If the amount is invalid or if ``from_`` has insufficient funds.
+    TypeError
+        If the amount is not an `int`.
 
     """
+    if not isinstance(amount, int):
+        raise TypeError("Transfer amount must be of type int, not {}.".format(type(amount)))
     if _invalid_amount(amount):
         raise ValueError("Invalid transfer amount {} <= 0".format(amount))