# Buggy code
def request(self, verb, url, payload=None, multipart=None, *, files=None, reason=None):
    headers = {}
    data = None
    files = files or []
    if payload:
        headers["Content-Type"] = "application/json"
        data = utils.to_json(payload)

    if reason:
        headers["X-Audit-Log-Reason"] = _uriquote(reason, safe="/ ")

    if multipart is not None:
        data = {"payload_json": multipart.pop("payload_json")}

    for tries in range(5):
        for file in files:
            file.reset(seek=tries)

        r = self.session.request(verb, url, headers=headers, data=data, files=multipart)
        r.encoding = "utf-8"
        # Coerce empty responses to return None for hygiene purposes
        response = r.text or None

        # compatibility with aiohttp
        r.status = r.status_code

        if r.headers["Content-Type"] == "application/json":
            response = json.loads(response)

        # check if we have rate limit header information
        remaining = r.headers.get("X-Ratelimit-Remaining")
        if remaining == "0" and r.status != 429 and self.sleep:
            delta = utils._parse_ratelimit_header(r)
            time.sleep(delta)

        if 300 > r.status >= 200:
            return response

        # we are being rate limited
        if r.status == 429:
            if self.sleep:
                retry_after = response["retry_after"] / 1000.0
                time.sleep(retry_after)
                continue
            else:
                raise HTTPException(r, response)

        if self.sleep and r.status in (500, 502):
            time.sleep(1 + tries * 2)
            continue

        if r.status == 403:
            raise Forbidden(r, response)
        elif r.status == 404:
            raise NotFound(r, response)
        else:
            raise HTTPException(r, response)
    # no more retries
    raise HTTPException(r, response)


# Traceback (KeyError)
Traceback (most recent call last):
File "C:/Users/User/py/donationbot/webhook_bug.py", line 21, in <module>
asyncio.get_event_loop().run_until_complete(test())
File "C:\Users\User\AppData\Local\Programs\Python\Python37-32\lib\asyncio\base_events.py", line 584, in run_until_complete
return future.result()
File "C:/Users/User/py/donationbot/webhook_bug.py", line 19, in test
await asyncio.gather(*tasks)
File "C:/Users/User/py/donationbot/webhook_bug.py", line 9, in suppress_exc
await webhook.send("test")
File "C:\Users\User\.virtualenvs\donationbot\lib\site-packages\discord\webhook.py", line 236, in handle_execution_response
data = await response
File "C:\Users\User\.virtualenvs\donationbot\lib\site-packages\discord\webhook.py", line 218, in request
retry_after = response['retry_after'] / 1000.0
KeyError: 'retry_after'

# Fixed code
def request(self, verb, url, payload=None, multipart=None, *, files=None, reason=None):
    headers = {}
    data = None
    files = files or []
    if payload:
        headers["Content-Type"] = "application/json"
        data = utils.to_json(payload)

    if reason:
        headers["X-Audit-Log-Reason"] = _uriquote(reason, safe="/ ")

    if multipart is not None:
        data = {"payload_json": multipart.pop("payload_json")}

    for tries in range(5):
        for file in files:
            file.reset(seek=tries)

        r = self.session.request(verb, url, headers=headers, data=data, files=multipart)
        r.encoding = "utf-8"
        # Coerce empty responses to return None for hygiene purposes
        response = r.text or None

        # compatibility with aiohttp
        r.status = r.status_code

        if r.headers["Content-Type"] == "application/json":
            response = json.loads(response)

        # check if we have rate limit header information
        remaining = r.headers.get("X-Ratelimit-Remaining")
        if remaining == "0" and r.status != 429 and self.sleep:
            delta = utils._parse_ratelimit_header(r)
            time.sleep(delta)

        if 300 > r.status >= 200:
            return response

        # we are being rate limited
        if r.status == 429:
            if self.sleep:
                if not r.headers.get("Via"):
                    # Banned by Cloudflare more than likely.
                    raise HTTPException(r, data)

                retry_after = response["retry_after"] / 1000.0
                time.sleep(retry_after)
                continue
            else:
                raise HTTPException(r, response)

        if self.sleep and r.status in (500, 502):
            time.sleep(1 + tries * 2)
            continue

        if r.status == 403:
            raise Forbidden(r, response)
        elif r.status == 404:
            raise NotFound(r, response)
        else:
            raise HTTPException(r, response)
    # no more retries
    raise HTTPException(r, response)