我相信这应该是一个很容易修复的错误，只要我能找到它在哪里。这是来自 Flask 应用程序的错误：
11:58:18 web.1 | ERROR:xxxxxx.core:Exception on / [GET]
11:58:18 web.1 | Traceback (most recent call last):
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask/app.py", line 1817, in wsgi_app
11:58:18 web.1 | response = self.full_dispatch_request()
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
11:58:18 web.1 | rv = self.handle_user_exception(e)
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
11:58:18 web.1 | reraise(exc_type, exc_value, tb)
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
11:58:18 web.1 | rv = self.dispatch_request()
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask/app.py", line 1461, in dispatch_request
11:58:18 web.1 | return self.view_functions[rule.endpoint](**req.view_args)
11:58:18 web.1 | File "xxxxxxx/web.py", line 202, in home
11:58:18 web.1 | d = {'featured': cached_apps.get_featured_front_page(),
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask_cache/__init__.py", line 245, in decorated_function
11:58:18 web.1 | rv = f(*args, **kwargs)
11:58:18 web.1 | File "/Users/xxxxxxx/Desktop/PythonProjects/xxxxxx/xxxxxx2/xxxxxxx/cache/apps.py", line 35, in get_featured_front_page
11:58:18 web.1 | results = db.engine.execute(sql)
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask_sqlalchemy/__init__.py", line 780, in engine
11:58:18 web.1 | return self.get_engine(self.get_app())
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask_sqlalchemy/__init__.py", line 797, in get_engine
11:58:18 web.1 | return connector.get_engine()
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask_sqlalchemy/__init__.py", line 470, in get_engine
11:58:18 web.1 | self._sa.apply_driver_hacks(self._app, info, options)
11:58:18 web.1 | File "/Library/Python/2.7/site-packages/flask_sqlalchemy/__init__.py", line 739, in apply_driver_hacks
11:58:18 web.1 | if info.drivername.startswith('mysql'):
11:58:18 web.1 | AttributeError: 'NoneType' object has no attribute 'drivername'
根据我在网上查到的信息，问题似乎是我可能没有正确连接到数据库。应用在Heroku上运行良好，但在本地主机上运行时出现问题。
which psql：
/Applications/Postgres.app/Contents/MacOS/bin/psql
which postgres:
/Applications/Postgres.app/Contents/MacOS/bin/postgres
编辑：更多信息
alembic.ini文件的一部分：
[alembic]
# path to migration scripts
script_location = alembic
# template used to generate migration files
# file_template = %%(rev)s_%%(slug)s
# under Heroku, the line below needs to be inferred from
# the environment
sqlalchemy.url = postgres://xxxxxxxxxx:xxxxxxxxxxxx@xxxxxx.compute-1.amazonaws.com:5432/xxxxxxxxx
# Logging configuration
[loggers]
keys = root,sqlalchemy,alembic
我有一个简短的脚本，会产生相同的错误：
我运行 python cli.py db_create
在
#!/usr/bin/env python
import os
import sys
import optparse
import inspect
import xxxxxxx.model as model
from xxxxxx.core import db
import xxxxx.web as web
from alembic.config import Config
from alembic import command
def setup_alembic_config():
if "DATABASE_URL" not in os.environ:
alembic_cfg = Config("alembic.ini")
else:
dynamic_filename = "alembic-heroku.ini"
with file("alembic.ini.template") as f:
with file(dynamic_filename, "w") as conf:
for line in f.readlines():
if line.startswith("sqlalchemy.url"):
conf.write("sqlalchemy.url = %s\n" %
os.environ['DATABASE_URL'])
else:
conf.write(line)
alembic_cfg = Config(dynamic_filename)
command.stamp(alembic_cfg, "head")
def db_create():
'''Create the db'''
db.create_all()
# then, load the Alembic configuration and generate the
# version table, "stamping" it with the most recent rev:
setup_alembic_config()
# finally, add a minimum set of categories: Volunteer Thinking, Volunteer Sensing, Published and Draft
categories = []
categories.append(model.Category(name="Thinking",
short_name='thinking',
description='Volunteer Thinking apps'))
categories.append(model.Category(name="Volunteer Sensing",
short_name='sensing',
description='Volunteer Sensing apps'))
db.session.add_all(categories)
db.session.commit()
然后我得到：
Traceback (most recent call last):
File "cli.py", line 111, in <module>
_main(locals())
File "cli.py", line 106, in _main
_methods[method](*args[1:])
File "cli.py", line 33, in db_create
db.create_all()
File "/Library/Python/2.7/site-packages/flask_sqlalchemy/__init__.py", line 856, in create_all
self._execute_for_all_tables(app, bind, 'create_all')
File "/Library/Python/2.7/site-packages/flask_sqlalchemy/__init__.py", line 848, in _execute_for_all_tables
op(bind=self.get_engine(app, bind), tables=tables)
File "/Library/Python/2.7/site-packages/flask_sqlalchemy/__init__.py", line 797, in get_engine
return connector.get_engine()
File "/Library/Python/2.7/site-packages/flask_sqlalchemy/__init__.py", line 470, in get_engine
self._sa.apply_driver_hacks(self._app, info, options)
File "/Library/Python/2.7/site-packages/flask_sqlalchemy/__init__.py", line 739, in apply_driver_hacks
if info.drivername.startswith('mysql'):
AttributeError: 'NoneType' object has no attribute 'drivername'