Default AUTH_MECHANISM

[markunsworth]

Sets default AUTH_MECHANISM values when using non URI configuration method.

Without this, trying to configure pymongo using a configuration prefix causes a KeyError

(Now with added tests)

[dcrosta]

I don't quite follow why this didn't work with a custom prefix, do you understand that?

[markunsworth]

If you specify any auth params(user/pass) it tries to get the
auth_mechanism from the app config, but if you haven't set it then you get
a key error as there is no default.

It's also the case when you don't use a custom prefix (have also added a test for this).

Error
Traceback (most recent call last):
  File "/usr/lib/python2.7/unittest/case.py", line 329, in run
    testMethod()
  File "/home/mark/development/flask-pymongo/tests/test_config.py", line 171, in test_missing_auth_mechanism_in_nonprefixed_config
    mongo = flask_pymongo.PyMongo(self.app)
  File "/home/mark/development/flask-pymongo/flask_pymongo/__init__.py", line 97, in __init__
    self.init_app(app, config_prefix)
  File "/home/mark/development/flask-pymongo/flask_pymongo/__init__.py", line 279, in init_app
    auth_mechanism = app.config[key('AUTH_MECHANISM')]
KeyError: 'MONGO_AUTH_MECHANISM'

[dcrosta]

Is the else ever going to be hit? I suspect you mean if pymongo.version_tuple[0] == 2: here and L196?

EDIT: oh, right, I need coffee. this is a little confusing so I'd slightly prefer if you would make this ">= 3" to avoid my brain's bugs.

[markunsworth]

sure - i actually copied an earlier test, so should I update that one too

[dcrosta]

Ah, so it is -- OK, I don't love that, but won't hold this up any more.

[dcrosta]

Thanks for the fix here!