在下面这段代码中，没有考虑没有获取到用户email的情况。我用自己的GitHub账号试了一下，我的email是保密的，在获取远程应用资源的时候，就没有获取到email，从而报错了。
@oauth_bp.route('/callback/<provider_name>')
def oauth_callback(provider_name):
if provider_name not in providers.keys():
abort(404)
provider = providers[provider_name]
response = provider.authorized_response()
if response is not None:
if provider_name == 'twitter':
access_token = response.get('oauth_token'), response.get('oauth_token_secret')
else:
access_token = response.get('access_token')
else:
access_token = None
if access_token is None:
flash('Access denied, please try again.')
return redirect(url_for('auth.login'))
username, website, github, email, bio = get_social_profile(provider, access_token)
user = User.query.filter_by(email=email).first()
if user is None:
user = User(email=email, nickname=username, website=website,
github=github, bio=bio)
db.session.add(user)
db.session.commit()
login_user(user, remember=True)
return redirect(url_for('chat.profile'))
login_user(user, remember=True)
return redirect(url_for('chat.home'))
