Support Pymongo 3

[furushchev]

This pull request contains:

• Fixes check_connection_to_mongod doesn't work with more recent versions of pymongo #196
  • Keeps compatibility with PyMongo 3.X ( c.f. http://api.mongodb.com/python/3.5.1/migrate-to-pymongo3.html )
• Minor fix
  • Uses rospy.logerr for error log instead of print to see error on remote computers
  • config_manager.py: Fixed installation of on_shutdown handler which prevents function call before assigning class member.

[furushchev]

Just a comment:
It's better to test on ubuntu 14.04 (=indigo) / 16.04 (=kinetic) and with daemon / without daemon for make this package more reliable.

14.04 uses pymongo 2.6
16.04 uses pymongo 3.2

To test using daemon, test file should be like:

<launch>
  <!-- mostly copied from mongodb_store/tests/message_store.test -->
  <param name="mongodb_use_daemon" value="true" />
  <param name="mongodb_port" value="27017" />
  <param name="mongodb_host" value="localhost" />

  <!--
  <node name="mongo_server" pkg="mongodb_store" type="mongodb_server.py">
    <param name="test_mode" value="true"/>
  </node>
  -->

  <node name="message_store" pkg="mongodb_store" type="message_store_node.py"/>

  <!-- rosout and diagnostic topic logger -->
  <!-- <node name="diagnostics_logger" pkg="strands_diagnostics" type="logger"/> -->
  
  <test test-name="test_messagestore" pkg="mongodb_store" type="test_messagestore.py" />

</launch>

[hawesie]

Thanks for the code!

@furushchev please can you explain the comment above about testing with different configurations? I don't quite follow it.

[furushchev]

@hawesie We currently use mongodb in 2 ways: using mongodb_server.py which spawns mongod instance or using system mongod (I called daemon in the previous comment) and in client side, there are two logics to check if mongodb server is alive or not for both cases. So we need to check both cases.
Also this package is released for indigo and kinetic which is run on ubuntu 14.04 / 16.04 respectively so it is better to test on both OS versions.
So my suggestion is to test on env:

#	Ubuntu	ROS	mongodb server
1	14.04	indigo	mongodb_server.py
2	14.04	indigo	system mongod
3	16.04	kinetic	mongodb_server.py
4	16.04	kinetic	system mongod

[hawesie]

Created a new issue for this in #208