query backends from installed packages

[edoput]

Hi all,

this will solve a problem that I had last summer during GSOC. Using entry_points in the definition
of setup.py we can query possible backends for use in netjsonconfig in other packages instead of having long-lived branches.

This is an example for a setup.py using the entry_points directive

from setuptools import setup, find_packages                                                                                                           
                                                                                                                                                      
setup(                                                                                                                                                
    name='airos',                                                                                                                                  
    version='0.0.0',                                                                                                                                  
    description='AirOS backend for netjsonconfig',                                                                                                                          
    packages=find_packages(),                                                                                                                         
    entry_points={                                                                                                                                    
        'netjsonconfig.backends': [                                                                                                                   
            'airos=netjsonconfig-airos.backend:AirOsBackend',                                                                                                    
        ]                                                                                                                                             
    }                                                                                                                                                 
) 

[coveralls]

Coverage remained the same at 99.931% when pulling 2bf557c on edoput:master into 11cfed1 on openwisp:master.

[coveralls]

Coverage remained the same at 99.931% when pulling 1511fc1 on edoput:master into 11cfed1 on openwisp:master.

[edoput]

This is an example backend as an external package that when installed along with netjsonconfig will let the user choose the example backend directly when using netjsonconfig

[redhog]

I greatly support this patch as it's The Right Way To Do it :P Please merge :)

[redhog]

Shouldn't this rather use the python logging framework?

[edoput]

in the grand scheme of integrating with openwisp-contoller it should use whatever openwisp-config is using? I don't really know what is the correct way to log this but I didn't want crash to propagate to netjsonconfig when loading. Moreover loggin requires to choose a target (console, file, syslog, ...) and a level and I'm not sure which should they be,

[redhog]

django-netjsonconfig/utils.py:9 uses

import logging
logger = logging.getLogger(__name__)
logger.warning("Grrrrrr")

[edoput]

Ok I'll change this to be a logger on the console 👍

[edoput]

Let me know if there's anything else to do or I'll squash everything before merge

[redhog]

Looks good :)

[nemesifier]

@edoput great job 👍, thank you!