# Buggy code
async def debug(self, ctx, *, code):
    """Evaluate a statement of python code.

    The bot will always respond with the return value of the code.
    If the return value of the code is a coroutine, it will be awaited,
    and the result of that will be the bot's response.

    Note: Only one statement may be evaluated. Using certain restricted
    keywords, e.g. yield, will result in a syntax error. For multiple
    lines or asynchronous code, see [p]repl or [p]eval.

    Environment Variables:
        ctx      - command invokation context
        bot      - bot object
        channel  - the current channel object
        author   - command author's member object
        message  - the command's message object
        discord  - discord.py library
        commands - redbot.core.commands
        _        - The result of the last dev command.
    """
    env = {
        "bot": ctx.bot,
        "ctx": ctx,
        "channel": ctx.channel,
        "author": ctx.author,
        "guild": ctx.guild,
        "message": ctx.message,
        "asyncio": asyncio,
        "aiohttp": aiohttp,
        "discord": discord,
        "commands": commands,
        "_": self._last_result,
    }

    code = self.cleanup_code(code)

    try:
        compiled = self.async_compile(code, "<string>", "eval")
        result = await self.maybe_await(eval(compiled, env))
    except SyntaxError as e:
        await ctx.send(self.get_syntax_error(e))
        return
    except Exception as e:
        await ctx.send(box("{}: {!s}".format(type(e).__name__, e), lang="py"))
        return

    self._last_result = result
    result = self.sanitize_output(ctx, str(result))

    await ctx.send_interactive(self.get_pages(result), box_lang="py")


# Traceback (KeyError)
Traceback (most recent call last):
File "/home/ubuntu/red-venv/lib/python3.8/site-packages/redbot/core/dev_commands.py", line 192, in _eval
result = await func()
File "<string>", line 3, in func
File "<string>", line 2, in <module>
File "/usr/lib/python3.8/typing.py", line 603, in __init__
def_mod = sys._getframe(1).f_globals['__name__']  # for pickling
KeyError: '__name__'

# Fixed code
async def debug(self, ctx, *, code):
    """Evaluate a statement of python code.

    The bot will always respond with the return value of the code.
    If the return value of the code is a coroutine, it will be awaited,
    and the result of that will be the bot's response.

    Note: Only one statement may be evaluated. Using certain restricted
    keywords, e.g. yield, will result in a syntax error. For multiple
    lines or asynchronous code, see [p]repl or [p]eval.

    Environment Variables:
        ctx      - command invokation context
        bot      - bot object
        channel  - the current channel object
        author   - command author's member object
        message  - the command's message object
        discord  - discord.py library
        commands - redbot.core.commands
        _        - The result of the last dev command.
    """
    env = {
        "bot": ctx.bot,
        "ctx": ctx,
        "channel": ctx.channel,
        "author": ctx.author,
        "guild": ctx.guild,
        "message": ctx.message,
        "asyncio": asyncio,
        "aiohttp": aiohttp,
        "discord": discord,
        "commands": commands,
        "_": self._last_result,
        "__name__": "__main__",
    }

    code = self.cleanup_code(code)

    try:
        compiled = self.async_compile(code, "<string>", "eval")
        result = await self.maybe_await(eval(compiled, env))
    except SyntaxError as e:
        await ctx.send(self.get_syntax_error(e))
        return
    except Exception as e:
        await ctx.send(box("{}: {!s}".format(type(e).__name__, e), lang="py"))
        return

    self._last_result = result
    result = self.sanitize_output(ctx, str(result))

    await ctx.send_interactive(self.get_pages(result), box_lang="py")