Fix TypeError when working with nested maps [JIRA: CLIENTS-417]

[nrvnrvn]

Fixes #401 (CLIENTS-349)

[hazen]

@nicorevin Could you please add a test case for your change? That would help me to verify. Thanks!

[nrvnrvn]

@javajolt I've added. See riak/tests/test_datatypes.py

[hazen]

Sorry, I missed it. Thanks!

[hazen]

👍 4dca64c

[hazen]

Looks like make lint failed. I'm guessing this is a newer version of pep8. I'll create a new PR to address that.

[hazen]

@borshop: merge

[nrvnrvn]

By the way, is it ok that modified attribute does not correspond with _updates and to_op() is None?
Even without this PR we have the following picture:

In [1]: from riak import RiakClient
In [2]: c = RiakClient()
In [3]: b = c.bucket_type('maps').bucket('wow')
In [4]: m = b.get('key')
In [5]: m.__dict__
Out[5]: 
{'_context': None,
 '_removes': set(),
 '_updates': {},
 '_value': {},
 'bucket': <RiakBucket 'maps'/'wow'>,
 'key': 'key'}

In [6]: m.maps['a']
Out[6]: <riak.datatypes.map.Map at 0x7fad9a294c50>
In [7]: m.flags['b']
Out[7]: <riak.datatypes.flag.Flag at 0x7fad99be8668>
In [8]: m.registers['c']
Out[8]: <riak.datatypes.register.Register at 0x7fad99be8278>
In [9]: m.counters['d']
Out[9]: <riak.datatypes.counter.Counter at 0x7fad99be8630>

In [10]: m._updates
Out[10]: 
{('a', 'map'): <riak.datatypes.map.Map at 0x7fad9a294c50>,
 ('b', 'flag'): <riak.datatypes.flag.Flag at 0x7fad99be8668>,
 ('c', 'register'): <riak.datatypes.register.Register at 0x7fad99be8278>,
 ('d', 'counter'): <riak.datatypes.counter.Counter at 0x7fad99be8630>}

In [11]: m.to_op()
# None

In [12]: m.modified
Out[12]: True

In [13]: m.context
# None

Of course if we call m.update() we catch No operation to send exception.
It means we know we have nothing to commit but we set the modified flag to true and keep the stack of local changes that will never ever be commited. Why?
P.S. Other datatypes meet the self.modified == (self.to_op() is not None) rule.

[nrvnrvn]

Updated pull request regarding my last comment.

[nrvnrvn]

Hi! Any updates?

[hazen]

Hmmm... Looks like it tried to get merged on April 16th, but I see no successful merge messages. Looks like our merge tool does not work on other repos. Let me look at your subsequent changes now, too.

[nrvnrvn]

We've been successfully using this patch for more than half a year.
Any chances for this to be merged into upstream?