Fix TypeError

[ale-rt]

This fixes an error when trying to get from an OOBTree a non existent value and the key has a type that cannot be compared with the existing keys

[ale-rt]

On Python 3.6 I see this:

(Pdb) from BTrees.OOBTree import OOBTree
(Pdb) one = OOBTree()
(Pdb) one['1'] =1
(Pdb) one.get(1)
*** TypeError: '<' not supported between instances of 'str' and 'int'
(Pdb) one[1] =1
*** TypeError: '<' not supported between instances of 'str' and 'int'
(Pdb) two = OOBTree()
(Pdb) two[1] = 1
(Pdb) two.get('1')
*** TypeError: '<' not supported between instances of 'int' and 'str'
(Pdb) two['1'] = 1
*** TypeError: '<' not supported between instances of 'int' and 'str'

I wonder if OOBTree.get should be fixed.

[davisagli]

Isn't it a useful error to know that your code is trying to query using the wrong type, rather than silently ignoring the wrongly typed query?

[ale-rt]

This makes the behavior consistent with what you had on Python 2.7.
And in addition this fixes zopefoundation/Products.CMFUid#7 ;)

[hannosch]

I would add some kind of logging in this case. Something like:

LOG.error(
    '%s: query_index tried to look up key %s '
    'from index %s but key was of the wrong type.' %
        (self.__class__.__name__, repr(k), str(self.id)))

Since the code is in the query_index method, the error could happen as a result of bad user input and some upstream code not doing enough input validation. I'd not show a traceback to those users.

But as a developer the error log entry should still be helpful in finding the application level code problem. Some code is trying to query the index with a value of a wrong type after all. And likely this is bad old code, which so far failed silently or behaved unpredictably in the past.

[ale-rt]

I added a log line, thanks for reviewing @davisagli and @hannosch