title: How do I make an "add" command send an error if you put words in the expression?
body: <p>Here you have the code I made for the command :</p>
  
  <pre><code>#?dodaj
  @client.command()
  async def dodaj(ctx, a: int, b: int):
      if (a == int and b == int):
          await ctx.send(a + b)
      else:
          await ctx.send("Błąd : Nie mogłem obliczyc tego działania!")
  </code></pre>
  
  <p>I want to know what's wrong with this, because it won't work properly.</p>
  
  <p>Here's the error i'm getting by typing "?dodaj coś jeszcze" :</p>
  
  <pre><code>Ignoring exception in command dodaj:
  Traceback (most recent call last):
    File "C:\Users\PC\AppData\Local\Programs\Python\Python37-32\lib\site-packages\discord\ext\commands\core.py", line 370, in _actual_conversion
      return converter(argument)
  ValueError: invalid literal for int() with base 10: 'coś'
  
  The above exception was the direct cause of the following exception:
  
  Traceback (most recent call last):
    File "C:\Users\PC\AppData\Local\Programs\Python\Python37-32\lib\site-packages\discord\ext\commands\bot.py", line 863, in invoke
      await ctx.command.invoke(ctx)
    File "C:\Users\PC\AppData\Local\Programs\Python\Python37-32\lib\site-packages\discord\ext\commands\core.py", line 721, in invoke
      await self.prepare(ctx)
    File "C:\Users\PC\AppData\Local\Programs\Python\Python37-32\lib\site-packages\discord\ext\commands\core.py", line 685, in prepare
      await self._parse_arguments(ctx)
    File "C:\Users\PC\AppData\Local\Programs\Python\Python37-32\lib\site-packages\discord\ext\commands\core.py", line 599, in _parse_arguments
      transformed = await self.transform(ctx, param)
    File "C:\Users\PC\AppData\Local\Programs\Python\Python37-32\lib\site-packages\discord\ext\commands\core.py", line 455, in transform
      return await self.do_conversion(ctx, converter, argument, param)
    File "C:\Users\PC\AppData\Local\Programs\Python\Python37-32\lib\site-packages\discord\ext\commands\core.py", line 408, in do_conversion
      return await self._actual_conversion(ctx, converter, argument, param)
    File "C:\Users\PC\AppData\Local\Programs\Python\Python37-32\lib\site-packages\discord\ext\commands\core.py", line 379, in _actual_conversion
      raise BadArgument('Converting to "{}" failed for parameter "{}".'.format(name, param.name)) from exc
  discord.ext.commands.errors.BadArgument: Converting to "int" failed for parameter "a".
  </code></pre>
  
  <p>Also when I type "?dodaj 20 20" it should add the 20's but it sends the error message that can be seen in the else parameter, in the code.</p>