Pymongo aggregate does not return a cursor but an

I am writing a code using pymongo which uses the aggregation framework to save some data in other collection. The code is this:

from pymongo import MongoClient

def makeAggregate():
  print 'Making aggregation of commits..'

  commitsCollection = MongoClient("mongo-srv", 27017).gt.commits
  rankingCollection = MongoClient("mongo-srv", 27017).gt.commitsRanking

  pipe = [{'$unwind': '$commits'},{'$group':{"_id":"$_id", "picture": {"$first": "$picture"},'a':{'$sum':'$commits.a'},'d':{'$sum':'$commits.d'},'c':{'$sum':'$commits.c'}}}]
  cursor = commitsCollection.aggregate(pipeline=pipe)

  obj = next(cursor, None)
  while obj:
    rankingCollection.save(obj)
    obj = next(cursor, None)

makeAggregate()

The code works fine on my computer, but when I moved the script to a server, then the script failed, saying:

Traceback (most recent call last):
  File "aggregate.py", line 17, in <module>
    makeAggregate()
  File "aggregate.py", line 12, in makeAggregate
    obj = next(cursor, None)
TypeError: dict object is not an iterator

The command python --version returns

On my computer: Python 2.7.3

On the server Python 2.7.6

The command pip show pymongo returns

On my computer:

Usage: pip COMMAND [OPTIONS]
pip: error: No command by the name pip show
  (maybe you meant "pip install show")

(Executed pip install show but keeps saying this when running show..)

On the server:

Name: pymongo
Version: 2.7
Location: /usr/local/lib/python2.7/dist-packages/pymongo-2.7-py2.7-linux-x86_64.egg
Requires:

Running pymongo.version inside python gives me:

In my computer: 3.0

In the server 2.7

Maybe I have to update this? How can I do that?

Yes thats the issue,
Different version of Pymongo for Development and Production environment

In PyMongo 2.7 it returns : Dictionary

{u'ok': 1.0, u'result': [{u'count': 3, u'_id': u'cat'}, {u'count': 2, u'_id': u'dog'}, {u'count': 1, u'_id': u'mouse'}]}

Whereas in PyMongo 3.0 it returns : Cursor Object

{u'count': 3, u'_id': u'cat'}, {u'count': 2, u'_id': u'dog'}, {u'count': 1, u'_id': u'mouse'}

Refer Pymongo 2.7 Documentation
Refer Pymongo 3.0 Documentation
Changes made from PyMongo 2.7 to PyMongo 3.0

Pro-Tip : Use Virtual Environment for Python and create a Requirements Text File.So as you can install the same version of Python Library and it Dependencies in Local Development and in Production.

Refer Virtual Environment Python Package