Make common Python 2 and Python 3 compatible

[jayich]

treedict is not Python 3 compatible.

[fanmingyu212]

@aransfor I started a branch https://github.com/CampbellGroup/common/tree/mf/python_3_upgrading for python 2/3 compatibility. If using python 3, it will use pyqt5 and pyqt4 for python 2. I will first start upgrading the pulser and normalpmtflow.

[aransfor]

@fanmingyu212 , sounds good! How is it going to deal with pyqt4/pyqt5? Also do you know the status of pylabrad compatibility with Python3 or if anyone has fully switched?

[fanmingyu212]

@aransfor I planned to have a separate folder "client_py3" for python 3 clients. The servers would be compatible with python 2 and 3 simultaneously though. I just learned that the Martinis Group has switched to python 3. I think pylabrad is now compatible with python 3.6 (See https://github.com/labrad/pylabrad/blob/master/setup.py#L18).

[aransfor]

@fanmingyu212 are you guys up and running on Python3?

[fanmingyu212]

@aransfor Yes, we are. Most of the servers and clients we are using in common (pulser, script scanner, ixonServer) are compatible with python 3. I am working on upgrading all servers and clients that we use and will finish soon.

I am not able to upgrade all servers and clients in common to python 3 as we are not using some of them so we cannot test, but they should be similar to the other upgraded servers and clients.

[fanmingyu212]

https://github.com/CampbellGroup/common/tree/mf/python_3_upgrading upgrades several servers and clients to python 3.

Servers upgraded to python 3:

• Datavault
• iXonServer
• ws8_server
• NormalPMTFlow
• parameter_vault
• Pulser2
• script_scanner
• serial_server
• serialdeviceserver

Python 3 clients added:

• ws8_client
• PMT_control
• Pulser2_DDS
• some uis in qtui
• script_scanner_gui
• connections

[fanmingyu212]

General methods I used to port servers to python 3:

• run 2to3 tool to fix any syntax issues
• check str / bytes conversions (different for python 2 and 3 and 2to3 cannot find all of problems)
• labrad settings "s" parameter is string in both python 2 and 3, but it is byte string in python 2 and unicode string in python 3.

General methods for porting clients to python 3:

• Use PyQt5 instead of PyQt4. In PyQt5 many classes / modules are reordered, e.g. many QtGui submodules are now in QtWidgets.
• Similar with above about str / bytes.