首先，请确保您已经更新了客户端库。我不确定您运行的是哪个版本，但库大约一年前就已修复。
然后拆下端口。

"redirect_uris":["http://localhost"]

第三次
如果这不起作用，这里是我的视频样本。插入它应该开箱即用。

#   To install the Google client library for Python, run the following command:
#   pip install --upgrade google-api-python-client google-auth-httplib2 google-auth-oauthlib

from __future__ import print_function

import os.path

import google.auth.exceptions
from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import InstalledAppFlow
from googleapiclient.discovery import build
from googleapiclient.errors import HttpError
from googleapiclient.http import MediaFileUpload

# If modifying these scopes, delete the file token.json.
SCOPES = ['https://www.googleapis.com/auth/youtube']

def main():

    """Shows basic usage of the YouTube v3 API.
    Uploads a private video to YouTube
    """
    creds = None
    # The file token.json stores the user's access and refresh tokens, and is
    # created automatically when the authorization flow completes for the first
    # time.
    if os.path.exists('token.json'):
        try:
            creds = Credentials.from_authorized_user_file('token.json', SCOPES)
            creds.refresh(Request())
        except google.auth.exceptions.RefreshError as error:
            # if refresh token fails, reset creds to none.
            #creds = None
            print(f'An error occurred: {error}')
    # If there are no (valid) credentials available, let the user log in.
    if not creds or not creds.valid:
        if creds and creds.expired and creds.refresh_token:
            creds.refresh(Request())
        else:
            flow = InstalledAppFlow.from_client_secrets_file(
                'C:\YouTube\dev\credentials.json', SCOPES)
            creds = flow.run_local_server(port=0)
        # Save the credentials for the next run
        with open('token.json', 'w') as token:
            token.write(creds.to_json())

    try:
        service = build('youtube', 'v3', credentials=creds)

        body = dict(
            snippet=dict(
                title="Test",
                description="test",
                tags="tes"
            ),
            status=dict(
                privacyStatus="private"
            )
        )

        media = MediaFileUpload("dummyvideo.mkv", chunksize=-1, resumable=True)

        results = service.videos().insert(
                part=",".join(body.keys()),
                body=body,
                media_body=media).execute()
        print(F'video ID: {results.get("id")}')

    except HttpError as error:
        # TODO(developer) - Handle errors from drive API.
        print(f'An error occurred: {error}')

if __name__ == '__main__':
    main()

google api python客户端的版本

我正在运行这些版本的相关google apis python库。

pip list

google-api-core          2.10.1
google-api-python-client 2.62.0
requests-oauthlib        1.3.1

我认为oauthlib可能也是其中的一部分。